%23%23%20Work%20of%20this%20course%20is%20in%20progress%0A%0A%0AAre%20you%20ready%20to%20take%20your%20web%20development%20skills%20to%20the%20next%20level%20with%20Golang%3F%20This%20course%20is%20designed%20to%20provide%20a%20comprehensive%20introduction%20to%20building%20web%20applications%20with%20the%20Go%20programming%20language.%0A%0A%0AYou'll%20learn%20how%20to%20use%20the%20powerful%20features%20of%20Go%20to%20build%20efficient%20and%20scalable%20web%20applications.%20From%20setting%20up%20a%20development%20environment%20to%20implementing%20security%20and%20testing%2C%20you'll%20get%20hands-on%20experience%20building%20real-world%20web%20applications.%0A%0A%0AThrough%20a%20combination%20of%20lectures%2C%20demos%2C%20and%20hands-on%20exercises%2C%20you'll%20learn%20how%20to%3A%0A%0A%0A*%20Set%20up%20a%20development%20environment%20for%20building%20web%20applications%20with%20Go%0A*%20Use%20the%20net%2Fhttp%20package%20to%20build%20web%20servers%20and%20handle%20HTTP%20requests%0A*%20Implement%20routing%2C%20middleware%2C%20and%20handlers%20to%20build%20flexible%20and%20modular%20web%20applications%0A*%20Use%20the%20Gorilla%20toolkit%20to%20add%20additional%20features%20to%20your%20web%20applications%2C%20such%20as%20websockets%20and%20sessions%0A*%20Implement%20security%20measures%20such%20as%20SSL%2FTLS%20and%20OAuth%20to%20protect%20your%20web%20application%0A*%20Test%20and%20debug%20your%20web%20applications%20to%20ensure%20they%20are%20reliable%20and%20performant%0A%0A%0ABy%20the%20end%20of%20this%20course%2C%20you'll%20have%20the%20skills%20and%20knowledge%20to%20build%20robust%20and%20efficient%20web%20applications%20with%20Go.

%60%60%60go%0Apackage%20main%0A%0Aimport%20%22fmt%22%0A%0Afunc%20main()%20%7B%0A%09fmt.println(%22Hello%20World!%22)%0A%7D%0A%60%60%60

Hello World

Go%20is%20a%20statically-typed%20language%2C%20which%20means%20that%20the%20type%20of%20a%20variable%20must%20be%20specified%20at%20the%20time%20of%20its%20declaration.%20The%20language%20provides%20a%20number%20of%20basic%20data%20types%2C%20including%3A%0A%0A*%20%60int%60%2C%20%60int8%60%2C%20%60int16%60%2C%20%60int32%60%2C%20and%20%60int64%60%20for%20representing%20signed%20integers%20of%20different%20sizes%0A*%20%60uint%60%2C%20%60uint8%60%2C%20%60uint16%60%2C%20%60uint32%60%2C%20and%20%60uint64%60%20for%20representing%20unsigned%20integers%20of%20different%20sizes%0A*%20%60float32%60%20and%20%60float64%60%20for%20representing%20floating-point%20numbers%0A*%20%60complex64%60%20and%20%60complex128%60%20for%20representing%20complex%20numbers%0A*%20%60bool%60%20for%20representing%20boolean%20values%20(true%20or%20false)%0A*%20%60string%60%20for%20representing%20string%20values%0A%0AIn%20addition%20to%20these%20basic%20types%2C%20Go%20also%20provides%20several%20composite%20types%2C%20which%20are%20used%20to%20represent%20more%20complex%20data%20structures.%20These%20include%3A%0A%0A*%20%60array%60%20for%20representing%20fixed-length%20arrays%20of%20values%0A*%20%60slice%60%20for%20representing%20dynamic%20arrays%20of%20values%0A*%20%60map%60%20for%20representing%20key-value%20pairs%0A*%20%60struct%60%20for%20representing%20complex%20data%20structures%20with%20named%20fields%0A*%20%60pointer%60%20for%20representing%20a%20reference%20to%20a%20memory%20location%0A*%20%60function%60%20for%20representing%20a%20function%20or%20method%0A%0AIt's%20important%20to%20note%20that%20Go%20is%20a%20type-safe%20language%2C%20which%20means%20that%20it%20will%20not%20allow%20you%20to%20perform%20operations%20on%20values%20of%20different%20types%20unless%20they%20are%20explicitly%20converted.%20For%20example%2C%20you%20cannot%20add%20an%20integer%20to%20a%20string%20unless%20you%20first%20convert%20the%20integer%20to%20a%20string.

Data Types

%23%23%20Using%20conditions%20in%20Go%0A%0AIn%20Go%2C%20we%20can%20use%20the%20%60if%60%20statement%20to%20execute%20a%20block%20of%20code%20only%20if%20a%20certain%20condition%20is%20true.%20For%20example%3A%0A%0A%60%60%60go%0Aif%20x%20%3E%2010%20%7B%0A%20%20fmt.Println(%22x%20is%20greater%20than%2010%22)%0A%7D%0A%60%60%60%0A%0AWe%20can%20also%20include%20an%20else%20clause%20to%20execute%20a%20different%20block%20of%20code%20if%20the%20condition%20is%20false%3A%0A%0A%60%60%60go%0Aif%20x%20%3E%2010%20%7B%0A%20%20fmt.Println(%22x%20is%20greater%20than%2010%22)%0A%7D%20else%20%7B%0A%20%20fmt.Println(%22x%20is%20not%20greater%20than%2010%22)%0A%7D%0A%60%60%60%0A%0AWe%20can%20even%20include%20an%20additional%20%60else%20if%60%20clause%20to%20check%20for%20multiple%20conditions%3A%0A%0A%60%60%60go%0Aif%20x%20%3E%2010%20%7B%0A%20%20fmt.Println(%22x%20is%20greater%20than%2010%22)%0A%7D%20else%20if%20x%20%3C%200%20%7B%0A%20%20fmt.Println(%22x%20is%20less%20than%200%22)%0A%7D%20else%20%7B%0A%20%20fmt.Println(%22x%20is%20between%200%20and%2010%22)%0A%7D%0A%60%60%60%0A%0A%23%23%20Using%20loops%20in%20Go%0A%0AIn%20Go%2C%20we%20can%20use%20the%20for%20loop%20to%20execute%20a%20block%20of%20code%20multiple%20times.%20There%20are%20three%20forms%20of%20the%20for%20loop%3A%0A%0A%60%60%60go%0Afor%20i%20%3C%2010%20%7B%0A%20%20fmt.Println(i)%0A%20%20i%2B%2B%0A%7D%0A%60%60%60%0A%0A%23%23%23%20The%20traditional%20form%0A%0AThis%20form%20of%20the%20for%20loop%20is%20similar%20to%20the%20for%20loop%20in%20other%20languages.%20It%20includes%20an%20initialization%20statement%2C%20a%20condition%2C%20and%20an%20increment%20statement%3A%0A%0A%60%60%60go%0Afor%20i%20%3A%3D%200%3B%20i%20%3C%2010%3B%20i%2B%2B%20%7B%0A%20%20fmt.Println(i)%0A%7D%0A%60%60%60%0A%0A%23%23%23%20The%20range%20form%0A%0AThis%20form%20of%20the%20for%20loop%20is%20used%20to%20iterate%20over%20a%20range%20of%20values%2C%20such%20as%20the%20elements%20in%20an%20array%20or%20slice.%20It%20returns%20the%20index%20and%20value%20of%20each%20element%20in%20the%20range%3A%0A%0A%60%60%60go%0Anumbers%20%3A%3D%20%5B%5Dint%7B1%2C%202%2C%203%2C%204%2C%205%7D%0Afor%20i%2C%20value%20%3A%3D%20range%20numbers%20%7B%0A%20%20fmt.Println(%22Index%3A%22%2C%20i%2C%20%22Value%3A%22%2C%20value)%0A%7D%0A%60%60%60%0A%0ABy%20using%20conditions%20and%20loops%2C%20we%20can%20control%20the%20flow%20of%20our%20Go%20programs%20and%20write%20more%20powerful%20and%20efficient%20code.

Conditions & Loops

In%20Go%2C%20a%20function%20is%20a%20block%20of%20code%20that%20performs%20a%20specific%20task%20and%20can%20be%20called%20from%20other%20parts%20of%20your%20program.%20Functions%20can%20accept%20input%20parameters%20and%20return%20output%20values%2C%20making%20them%20a%20powerful%20tool%20for%20organizing%20and%20reusing%20code.%0A%0A%23%23%20Defining%20a%20function%20in%20Go%0A%0ATo%20define%20a%20function%20in%20Go%2C%20we%20use%20the%20func%20keyword%20followed%20by%20the%20name%20of%20the%20function%20and%20a%20list%20of%20parameters.%20The%20parameters%20are%20a%20list%20of%20variables%20separated%20by%20commas%20and%20enclosed%20in%20parentheses.%20The%20function%20body%20is%20enclosed%20in%20curly%20braces%20and%20contains%20the%20code%20that%20will%20be%20executed%20when%20the%20function%20is%20called.%0A%0AHere's%20an%20example%20of%20a%20simple%20function%20that%20accepts%20two%20integers%20as%20input%20and%20returns%20their%20sum%3A%0A%0A%60%60%60go%0Afunc%20add(x%20int%2C%20y%20int)%20int%20%7B%0A%20%20return%20x%20%2B%20y%0A%7D%0A%60%60%60%0A%0AIn%20Go%2C%20we%20can%20also%20define%20a%20function%20with%20multiple%20return%20values.%20For%20example%2C%20here's%20a%20function%20that%20returns%20both%20the%20quotient%20and%20remainder%20of%20a%20division%20operation%3A%0A%0A%60%60%60go%0Afunc%20divmod(x%20int%2C%20y%20int)%20(int%2C%20int)%20%7B%0A%20%20quotient%20%3A%3D%20x%20%2F%20y%0A%20%20remainder%20%3A%3D%20x%20%25%20y%0A%20%20return%20quotient%2C%20remainder%0A%7D%0A%60%60%60%0A%0A%23%23%20Calling%20a%20function%20in%20Go%0A%0ATo%20call%20a%20function%20in%20Go%2C%20we%20simply%20use%20its%20name%20followed%20by%20a%20list%20of%20arguments%20enclosed%20in%20parentheses.%20The%20arguments%20are%20the%20values%20that%20will%20be%20passed%20to%20the%20function%20as%20input%20parameters.%0A%0AHere's%20an%20example%20of%20calling%20the%20add%20function%20we%20defined%20earlier%3A%0A%0A%60%60%60go%0Aresult%20%3A%3D%20add(3%2C%204)%0Afmt.Println(result)%20%20%2F%2F%20Output%3A%207%0A%60%60%60%0A%0AIf%20a%20function%20returns%20multiple%20values%2C%20we%20can%20use%20the%20_%20placeholder%20to%20ignore%20any%20values%20we%20don't%20need.%20For%20example%3A%0A%0A%60%60%60go%0Aquotient%2C%20_%20%3A%3D%20divmod(7%2C%202)%0Afmt.Println(quotient)%20%20%2F%2F%20Output%3A%203%0A%60%60%60%0A%0A%23%23%20Variadic%20functions%20in%20Go%0A%0AIn%20Go%2C%20we%20can%20define%20a%20function%20with%20a%20variable%20number%20of%20arguments%20by%20using%20the%20...%20operator%20in%20the%20parameter%20list.%20This%20is%20known%20as%20a%20variadic%20function.%0A%0AHere's%20an%20example%20of%20a%20variadic%20function%20that%20calculates%20the%20sum%20of%20an%20arbitrary%20number%20of%20integers%3A%0A%0A%60%60%60go%0Afunc%20sum(numbers%20...int)%20int%20%7B%0A%20%20total%20%3A%3D%200%0A%20%20for%20_%2C%20value%20%3A%3D%20range%20numbers%20%7B%0A%20%20%20%20total%20%2B%3D%20value%0A%20%20%7D%0A%20%20return%20total%0A%7D%0A%60%60%60%0A%0ATo%20call%20a%20variadic%20function%2C%20we%20simply%20pass%20in%20as%20many%20arguments%20as%20we%20need.%20For%20example%3A%0A%0A%60%60%60go%0Aresult%20%3A%3D%20sum(1%2C%202%2C%203%2C%204%2C%205)%0Afmt.Println(result)%20%20%2F%2F%20Output%3A%2015%0A%60%60%60%0A%0A%23%23%20Function%20closures%20in%20Go%0A%0AIn%20Go%2C%20we%20can%20create%20a%20closure%20by%20using%20a%20function%20literal%2C%20which%20is%20a%20function%20without%20a%20name%20that%20is%20immediately%20invoked.%20A%20closure%20is%20a%20function%20value%20that%20references%20variables%20from%20outside%20its%20body.%20When%20the%20closure%20is%20called%2C%20it%20has%20access%20to%20the%20variables%20in%20its%20environment.%0A%0AHere's%20an%20example%20of%20a%20closure%20that%20increments%20a%20counter%20variable%20each%20time%20it%20is%20called%3A%0A%0A%60%60%60go%0Acounter%20%3A%3D%200%0Aincrement%20%3A%3D%20func()%20int%20%7B%0A%20%20counter%2B%2B%0A%20%20return%20counter%0A%7D%0A%60%60%60%0A%0AWe%20can%20then%20call%20the%20closure%20as%20many%20times%20as%20we%20want%2C%20and%20it%20will%20always%20return%20the%20current%20value%20of%20the%20counter%3A%0A%0A%60%60%60go%0Afmt.Println(increment())%20%20%2F%2F%0A%60%60%60

Functions

Golang Basics

In%20Go%2C%20an%20array%20is%20a%20fixed-size%20collection%20of%20elements%20of%20the%20same%20type.%20Arrays%20are%20useful%20for%20storing%20a%20sequence%20of%20values%20that%20need%20to%20be%20stored%20and%20accessed%20in%20a%20specific%20order.%20In%20this%20blog%2C%20we%20will%20take%20a%20closer%20look%20at%20how%20to%20create%20and%20manipulate%20arrays%20in%20Go.%0A%0A%23%23%20Creating%20an%20array%20in%20Go%0A%0ATo%20create%20an%20array%20in%20Go%2C%20we%20use%20the%20%5Bsize%5Dtype%20syntax.%20The%20size%20parameter%20specifies%20the%20number%20of%20elements%20in%20the%20array%2C%20and%20the%20type%20parameter%20specifies%20the%20type%20of%20each%20element.%0A%0AHere's%20an%20example%20of%20creating%20an%20array%20of%20integers%20with%20a%20size%20of%205%3A%0A%0A%60%60%60go%0Avar%20numbers%20%5B5%5Dint%0A%60%60%60%0A%0AWe%20can%20also%20initialize%20the%20array%20with%20a%20list%20of%20values%3A%0A%0A%60%60%60go%0Anumbers%20%3A%3D%20%5B5%5Dint%7B1%2C%202%2C%203%2C%204%2C%205%7D%0A%60%60%60%0A%0AIf%20we%20omit%20the%20size%20parameter%2C%20Go%20will%20infer%20the%20size%20of%20the%20array%20based%20on%20the%20number%20of%20elements%20in%20the%20initialization%20list%3A%0A%0Anumbers%20%3A%3D%20%5B%5Dint%7B1%2C%202%2C%203%2C%204%2C%205%7D%0A%0A%23%23%23%20Accessing%20and%20modifying%20array%20elements%0A%0ATo%20access%20an%20element%20in%20an%20array%2C%20we%20use%20the%20index%20of%20the%20element%20in%20square%20brackets.%20The%20index%20starts%20at%200%20and%20goes%20up%20to%20the%20size%20of%20the%20array%20minus%201.%0A%0AHere's%20an%20example%20of%20accessing%20the%20first%20element%20in%20the%20numbers%20array%20we%20defined%20earlier%3A%0A%0A%60%60%60go%0Afmt.Println(numbers%5B0%5D)%20%20%2F%2F%20Output%3A%201%0A%60%60%60%0A%0AWe%20can%20also%20use%20a%20loop%20to%20iterate%20over%20all%20the%20elements%20in%20an%20array%3A%0A%0A%60%60%60go%0Afor%20i%2C%20value%20%3A%3D%20range%20numbers%20%7B%0A%20%20fmt.Println(%22Index%3A%22%2C%20i%2C%20%22Value%3A%22%2C%20value)%0A%7D%0A%60%60%60%0A%0ATo%20modify%20an%20element%20in%20an%20array%2C%20we%20simply%20assign%20a%20new%20value%20to%20the%20element%20using%20the%20index%3A%0A%0A%60%60%60go%0Anumbers%5B0%5D%20%3D%2010%0Afmt.Println(numbers%5B0%5D)%20%20%2F%2F%20Output%3A%2010%0A%60%60%60%0A%0A%23%23%20Slices%20in%20Go%0A%0AIn%20addition%20to%20arrays%2C%20Go%20also%20has%20a%20data%20type%20called%20a%20slice%2C%20which%20is%20a%20dynamically-sized%2C%20flexible%20view%20of%20an%20array.%20Slices%20are%20more%20common%20in%20Go%20than%20arrays%20because%20they%20are%20more%20convenient%20to%20use%20and%20more%20efficient.%0A%0ATo%20create%20a%20slice%2C%20we%20use%20the%20%5B%5Dtype%20syntax%20and%20initialize%20it%20with%20a%20list%20of%20values%3A%0A%0A%60%60%60go%0Anumbers%20%3A%3D%20%5B%5Dint%7B1%2C%202%2C%203%2C%204%2C%205%7D%0A%60%60%60%0A%0AWe%20can%20also%20create%20a%20slice%20from%20an%20existing%20array%20by%20using%20the%20%5Blow%3Ahigh%5D%20syntax%2C%20where%20low%20is%20the%20index%20of%20the%20first%20element%20and%20high%20is%20the%20index%20of%20the%20element%20after%20the%20last%20element%20we%20want%20to%20include%20in%20the%20slice.%0A%0AHere's%20an%20example%20of%20creating%20a%20slice%20from%20the%20numbers%20array%20we%20defined%20earlier%3A%0A%0A%60%60%60go%0Asubslice%20%3A%3D%20numbers%5B1%3A3%5D%0Afmt.Println(subslice)%20%20%2F%2F%20Output%3A%20%5B2%2C%203%5D%0A%60%60%60%0A%0AWe%20can%20also%20omit%20the%20low%20or%20high%20index%20to%20include%20all%20elements%20from%20the%20start%20or%20end%20of%20the%20array%2C%20respectively%3A%0A%0A%60%60%60go%0Asubslice%20%3A%3D%20numbers%5B%3A3%5D%20%20%2F%2F%20includes%20elements%20from%20index%200%20to%202%0Asubslice%20%3A%3D%20numbers%5B1%3A%5D%20%20%2F%2F%20includes%20elements%20from%20index%201%20to%20the%20end%0A%60%60%60%0A%0ATo%20modify%20a%20slice%2C%20we%20can%20use%20the%20same%20indexing%20and%20assignment%20syntax%20as%20we%20used%20for%20arrays.

Array & Slice

In%20Go%2C%20a%20map%20is%20a%20collection%20of%20key-value%20pairs%20that%20can%20be%20used%20to%20store%20and%20retrieve%20data%20efficiently.%20Maps%20are%20useful%20for%20storing%20data%20that%20needs%20to%20be%20associated%20with%20a%20unique%20key%2C%20such%20as%20a%20database%20of%20users%20with%20their%20corresponding%20email%20addresses.%0A%0A%23%23%20Creating%20a%20map%20in%20Go%0A%0ATo%20create%20a%20map%20in%20Go%2C%20we%20use%20the%20map%5BkeyType%5DvalueType%20syntax.%20The%20keyType%20parameter%20specifies%20the%20type%20of%20the%20keys%20in%20the%20map%2C%20and%20the%20valueType%20parameter%20specifies%20the%20type%20of%20the%20values.%0A%0AHere's%20an%20example%20of%20creating%20a%20map%20of%20strings%20to%20integers%3A%0A%0A%60%60%60go%0Avar%20numbers%20map%5Bstring%5Dint%0A%60%60%60%0A%0AWe%20can%20also%20initialize%20the%20map%20with%20a%20list%20of%20key-value%20pairs%3A%0A%0A%60%60%60go%0Anumbers%20%3A%3D%20map%5Bstring%5Dint%7B%22one%22%3A%201%2C%20%22two%22%3A%202%2C%20%22three%22%3A%203%7D%0A%60%60%60%0A%0A%23%23%23%20Accessing%20and%20modifying%20map%20elements%0A%0ATo%20access%20an%20element%20in%20a%20map%2C%20we%20use%20the%20index%20operator%20(%5B%5D)%20with%20the%20key%20of%20the%20element.%20If%20the%20key%20exists%20in%20the%20map%2C%20the%20corresponding%20value%20will%20be%20returned.%20If%20the%20key%20does%20not%20exist%2C%20the%20zero%20value%20of%20the%20value%20type%20will%20be%20returned.%0A%0AHere's%20an%20example%20of%20accessing%20the%20value%20of%20the%20%22one%22%20key%20in%20the%20numbers%20map%20we%20defined%20earlier%3A%0A%0A%60%60%60go%0Afmt.Println(numbers%5B%22one%22%5D)%20%20%2F%2F%20Output%3A%201%0A%60%60%60%0A%0ATo%20check%20if%20a%20key%20exists%20in%20a%20map%2C%20we%20can%20use%20the%20%2C%20ok%20form%20of%20the%20index%20operator.%20This%20will%20return%20a%20boolean%20value%20indicating%20whether%20the%20key%20exists%20in%20the%20map%2C%20as%20well%20as%20the%20value%20of%20the%20key%20if%20it%20exists.%0A%0A%60%60%60go%0Avalue%2C%20ok%20%3A%3D%20numbers%5B%22four%22%5D%0Aif%20!ok%20%7B%0A%20%20fmt.Println(%22Key%20does%20not%20exist%22)%0A%7D%20else%20%7B%0A%20%20fmt.Println(%22Value%3A%22%2C%20value)%0A%7D%0A%60%60%60%0A%0ATo%20add%20a%20new%20key-value%20pair%20to%20a%20map%2C%20we%20simply%20assign%20a%20value%20to%20a%20key%20that%20does%20not%20already%20exist%20in%20the%20map%3A%0A%0A%60%60%60go%0Anumbers%5B%22four%22%5D%20%3D%204%0Afmt.Println(numbers%5B%22four%22%5D)%20%20%2F%2F%20Output%3A%204%0A%60%60%60%0A%0ATo%20delete%20a%20key-value%20pair%20from%20a%20map%2C%20we%20can%20use%20the%20delete%20function%3A%0A%0A%60%60%60go%0Adelete(numbers%2C%20%22four%22)%0Avalue%2C%20ok%20%3A%3D%20numbers%5B%22four%22%5D%0Aif%20!ok%20%7B%0A%20%20fmt.Println(%22Key%20does%20not%20exist%22)%0A%7D%20else%20%7B%0A%20%20fmt.Println(%22Value%3A%22%2C%20value)%0A%7D%0A%60%60%60%0A%0A%23%23%23%20Iterating%20over%20a%20map%0A%0ATo%20iterate%20over%20the%20key-value%20pairs%20in%20a%20map%2C%20we%20can%20use%20a%20for%20loop%20with%20the%20range%20keyword.%20This%20will%20return%20the%20key%20and%20value%20of%20each%20pair%20in%20the%20map.%0A%0A%60%60%60go%0Afor%20key%2C%20value%20%3A%3D%20range%20numbers%20%7B%0A%20%20fmt.Println(%22Key%3A%22%2C%20key%2C%20%22Value%3A%22%2C%20value)%0A%7D%0A%60%60%60%0A%0AWe%20can%20also%20iterate%20over%20just%20the%20keys%20or%20values%20by%20using%20the%20blank%20identifier%20(_)%20in%20place%20of%20the%20unused%20variable.%0A%0A%60%60%60go%0Afor%20key%20%3A%3D%20range%20numbers%20%7B%0A%20%20fmt.Println(%22Key%3A%22%2C%20key)%0A%7D%0A%0Afor%20_%2C%20value%20%3A%3D%20range%20numbers%20%7B%0A%20%20fmt.Println(%22Value%3A%22%2C%20value)%0A%7D%0A%60%60%60%0A%0AIn%20Go%2C%20maps%20are%20reference%20types%2C%20meaning%20that%20when%20a%20map%20is%20assigned%20to%20a%20new%20variable%20or%20passed%20as%20an%20argument%20to%20a%20function%2C%20the%20new%20variable%20or%20function%20parameter%20refers%20to%20the%20same%20underlying%20map%20data.%20Any%20changes%20made%20to%20the%20map%20through%20the%20new%20variable%20or%20parameter%20will%20be%20reflected%20in%20the%20original%20map.%0A%0ATo%20illustrate%20this%20behavior%2C%20consider%20the%20following%20example%3A%0A%0A%60%60%60go%0Afunc%20addValue(numbers%20map%5Bstring%5Dint)%20%7B%0A%20%20numbers%5B%22four%22%5D%20%3D%204%0A%7D%0A%0Anumbers%20%3A%3D%20map%5Bstring%5Dint%7B%22one%22%3A%201%2C%20%22two%22%3A%202%2C%20%22three%22%3A%203%7D%0AaddValue(numbers)%0Afmt.Println(numbers)%20%20%2F%2F%20Output%3A%20map%5Bone%3A1%20two%3A2%20three%3A3%20four%3A4%5D%0A%60%60%60%0A%0AIn%20the%20example%20above%2C%20the%20addValue%20function%20adds%20a%20new%20key-value%20pair%20to%20the%20numbers%20map.%20Even%20though%20the%20numbers%20map%20is%20passed%20as%20an%20argument%20to%20the%20function%2C%20the%20changes%20made%20to%20the%20map%20within%20the%20function%20are%20reflected%20in%20the%20original%20map.%0A%0AIf%20we%20want%20to%20create%20a%20new%20copy%20of%20a%20map%2C%20we%20can%20use%20the%20copy%20function%20to%20create%20a%20new%20map%20with%20the%20same%20key-value%20pairs%20as%20the%20original%20map.%0A%0AnewNumbers%20%3A%3D%20make(map%5Bstring%5Dint)%0Acopy(newNumbers%2C%20numbers)%0A%0A%23%23%23%20Map%20literals%0A%0AIn%20Go%2C%20we%20can%20create%20a%20map%20literal%2C%20which%20is%20a%20shorthand%20notation%20for%20creating%20a%20map%20and%20initializing%20it%20with%20a%20list%20of%20key-value%20pairs.%20A%20map%20literal%20is%20created%20using%20the%20map%5BkeyType%5DvalueType%7Bkey%3A%20value%2C%20...%7D%20syntax.%0A%0AHere's%20an%20example%20of%20a%20map%20literal%3A%0A%0A%60%60%60go%0Anumbers%20%3A%3D%20map%5Bstring%5Dint%7B%22one%22%3A%201%2C%20%22two%22%3A%202%2C%20%22three%22%3A%203%7D%0A%60%60%60%0A%0AMap%20literals%20are%20convenient%20for%20creating%20small%20maps%20with%20a%20fixed%20set%20of%20key-value%20pairs.%20However%2C%20for%20larger%20maps%20or%20maps%20that%20need%20to%20be%20modified%20frequently%2C%20it%20is%20more%20efficient%20to%20use%20the%20make%20function%20to%20create%20the%20map%20and%20add%20elements%20to%20it%20as%20needed.

Golang Collection

In%20Go%2C%20a%20struct%20is%20a%20composite%20data%20type%20that%20groups%20together%20related%20values%20under%20a%20single%20name.%20Structs%20are%20useful%20for%20creating%20custom%20data%20types%20that%20can%20be%20used%20to%20represent%20complex%20data%20structures%2C%20such%20as%20a%20point%20on%20a%20coordinate%20plane%20or%20a%20database%20record.%20In%20this%20blog%2C%20we%20will%20take%20a%20closer%20look%20at%20how%20to%20define%20and%20use%20structs%20in%20Go.%0A%0A%23%23%20Defining%20a%20struct%20in%20Go%0A%0ATo%20define%20a%20struct%20in%20Go%2C%20we%20use%20the%20struct%20keyword%20followed%20by%20a%20list%20of%20fields%20inside%20curly%20braces.%20Each%20field%20consists%20of%20a%20name%20and%20a%20type%2C%20separated%20by%20a%20colon.%0A%0AHere's%20an%20example%20of%20a%20struct%20that%20represents%20a%20point%20on%20a%20coordinate%20plane%3A%0A%0A%60%60%60go%0Atype%20Point%20struct%20%7B%0A%20%20X%20float64%0A%20%20Y%20float64%0A%7D%0A%60%60%60%0A%0AWe%20can%20also%20define%20a%20struct%20with%20a%20list%20of%20field%20names%20and%20types%20on%20separate%20lines%3A%0A%0A%60%60%60go%0Atype%20Point%20struct%20%7B%0A%20%20X%20float64%0A%20%20Y%20float64%0A%7D%0A%60%60%60%0A%0A%23%23%20Creating%20a%20struct%20value%0A%0ATo%20create%20a%20struct%20value%2C%20we%20use%20the%20struct%7Bfield%20values%7D%20syntax.%20The%20field%20values%20are%20a%20list%20of%20values%20separated%20by%20commas%20and%20enclosed%20in%20curly%20braces.%20The%20values%20must%20be%20in%20the%20same%20order%20as%20the%20fields%20in%20the%20struct%20definition.%0A%0AHere's%20an%20example%20of%20creating%20a%20Point%20struct%20value%3A%0A%0A%60%60%60go%0Apoint%20%3A%3D%20Point%7B1.0%2C%202.0%7D%0A%60%60%60%0A%0AWe%20can%20also%20use%20the%20new%20function%20to%20create%20a%20pointer%20to%20a%20struct%20value%3A%0A%0A%60%60%60go%0Apoint%20%3A%3D%20new(Point)%0A%60%60%60%0A%0A%23%23%23%20Accessing%20struct%20fields%0A%0ATo%20access%20a%20field%20in%20a%20struct%2C%20we%20use%20the%20dot%20notation%20followed%20by%20the%20name%20of%20the%20field.%0A%0A%60%60%60go%0Afmt.Println(point.X)%20%20%2F%2F%20Output%3A%201.0%0A%60%60%60%0A%0AWe%20can%20also%20use%20the%20pointer%20notation%20(-%3E)%20to%20access%20a%20field%20in%20a%20struct%20through%20a%20pointer%3A%0A%0A%60%60%60go%0Apoint%20%3A%3D%20new(Point)%0Apoint.X%20%3D%201.0%0Apoint.%0A%60%60%60%0A%0A%23%23%20Class%20vs%20Structure%0A%0AThere%20is%20struct%20instead%20of%20class%20in%20go.%20And%20you%20can%20achieve%20the%20behavior%20of%20a%20class%20in%20go%20using%20struct.%20Let's%20see%20an%20example%2C%0A%0A%60%60%60java%0Apublic%20class%20Student()%20%7B%0A%20%20%20%20private%20String%20name%3B%0A%20%20%20%20private%20String%20dept%3B%0Apublic%20Student()%20%7B%0A%7D%0Apublic%20Student(String%20name%2C%20String%20dept)%7B%0A%20%20%20%20%20%20%20%20this.name%20%3D%20name%3B%0A%20%20%20%20%20%20%20%20this.dept%20%3D%20dept%3B%0A%20%20%20%20%7D%0Apublic%20String%20getName()%7B%0A%20%20%20%20%20%20%20%20return%20this.name%3B%0A%20%20%20%20%7D%0Apublic%20void%20setName(String%20name)%7B%0A%20%20%20%20%20%20%20%20this.name%20%3D%20name%3B%0A%20%20%20%20%7D%0Apublic%20String%20getDept()%7B%0A%20%20%20%20%20%20%20%20return%20this.dept%3B%0A%20%20%20%20%7D%0Apublic%20void%20setDept(String%20dept)%7B%0A%20%20%20%20%20%20%20%20this.dept%20%3D%20dept%3B%0A%20%20%20%20%7D%0A%7D%0A%60%60%60%0A%0AEquivalent%20code%20in%20go%2C%0A%0A%60%60%60go%0Atype%20Student%20struct%20%7B%0A%20name%20string%0A%20dept%20string%0A%7D%0Afunc%20NewStudent(name%20string%2C%20dept%20string)%20Student%20%7B%0A%20return%20Student%7B%0A%20%20name%3A%20name%2C%0A%20%20dept%3A%20dept%2C%0A%20%7D%0A%7D%0Afunc%20(s%20*Student)%20GetName()%20string%20%7B%0A%20return%20s.name%0A%7D%0Afunc%20(s%20*Student)%20SetName(name%20string)%20%7B%0A%20s.name%20%3D%20name%0A%7D%0Afunc%20(s%20*Student)%20GetDept()%20string%20%7B%0A%20return%20s.dept%0A%7D%0Afunc%20(s%20*Student)%20SetDept(dept%20string)%20%7B%0A%20s.dept%20%3D%20dept%0A%7D%0A%60%60%60%0A%0ANote%20%3A%20In%20go%20properties%20starts%20with%20anything%20other%20than%20uppercase%20is%20not%20accessible%20from%20outside%20of%20package.%0A%0A%23%23%20Inheritance%20vs%20Composition%0A%0A%60%60%60go%0Atype%20TA%20struct%20%7B%0A%20Student%0A%20_Courses%20%5B%5Dstring%0A%7D%0Afunc%20NewTA(name%20string%2C%20dept%20string%2C%20courses%20%5B%5Dstring)%20TA%20%7B%0A%20return%20TA%7B%0A%20%20Student%7B%0A%20%20%20name%3A%20name%2C%0A%20%20%20dept%3A%20dept%2C%0A%20%20%7D%2C%0A%20%20courses%2C%0A%20%7D%0A%7D%0Afunc%20(ta%20*TA)%20SetCourses(courses%20%5B%5Dstring)%20%7B%0A%20ta._Courses%20%3D%20courses%0A%7D%0Afunc%20(ta%20*TA)%20GetCourses()%20%5B%5Dstring%20%7B%0A%20return%20ta._Courses%0A%7D%0A%60%60%60%0A%0AComposition%20is%20a%20way%20of%20embedding%20one%20structure%20within%20another.%20In%20above%20example%20embedded%20Student%20structure%20in%20TA.%20And%20by%20this%20you%20can%20achieve%20behaviour%20of%20the%20embedded%20structure%20too.%0A%0A%23%23%20Encapsulation%0A%0AIn%20go%20fields%2C%20methods%2C%20structures%20name%20starts%20with%20anything%20other%20than%20uppercase%20are%20private%20by%20default%20from%20outside%20of%20package.%0Aconsider%20the%20above%20example.%0A%0A%23%23%20Polymorphism%0A%0A%60%60%60go%0Aimport%20%22fmt%22%0Atype%20DriverInfo%20interface%20%7B%0A%20GetInfo()%20string%0A%7D%0Atype%20Driver%20struct%20%7B%0A%20Name%20string%0A%7D%0Atype%20CarDriver%20struct%20%7B%0A%20Driver%0A%7D%0Atype%20MotorDriver%20struct%20%7B%0A%20Driver%0A%7D%0Afunc%20(d%20Driver)%20GetInfo()%20string%20%7B%0A%20return%20d.Name%20%2B%20%22%2C%20Driver%22%0A%7D%0Afunc%20(cd%20CarDriver)%20GetInfo()%20string%20%7B%0A%20return%20cd.Name%20%2B%20%22%2C%20CarDriver%22%0A%7D%0Afunc%20(md%20MotorDriver)%20GetInfo()%20string%20%7B%0A%20return%20md.Name%20%2B%20%22%2C%20MotorDriver%22%0A%7D%0Afunc%20main()%20%7B%0A%20d%20%3A%3D%20Driver%7BName%3A%20%22A%22%7D%0A%20cd%20%3A%3D%20CarDriver%7BDriver%7BName%3A%20%22B%22%7D%7D%0A%20md%20%3A%3D%20MotorDriver%7BDriver%7BName%3A%20%22C%22%7D%7D%0A%20fmt.Println(d.GetInfo())%0A%20fmt.Println(cd.GetInfo())%0A%20fmt.Println(md.GetInfo())%0A%7D%0A%60%60%60%0A%0AExample%20of%20method%20overriding.%20Go%20doesn%E2%80%99t%20support%20method%20overloading.%0A%0A%23%23%20Abstraction%0A%0AOne%20can%20achieve%20abstraction%20using%20**interface**.

Struct & Inheritance

In%20Go%2C%20an%20interface%20is%20a%20type%20that%20specifies%20a%20set%20of%20methods%20that%20a%20struct%20must%20implement%20in%20order%20to%20satisfy%20the%20interface.%20Interfaces%20are%20a%20way%20to%20define%20abstractions%20in%20Go%20and%20are%20used%20to%20decouple%20code%20and%20promote%20code%20reuse.%0A%0A%23%23%20Defining%20an%20interface%20in%20Go%0A%0ATo%20define%20an%20interface%20in%20Go%2C%20we%20use%20the%20type%20keyword%20followed%20by%20the%20name%20of%20the%20interface%20and%20a%20list%20of%20method%20signatures%20enclosed%20in%20curly%20braces.%20A%20method%20signature%20consists%20of%20the%20method%20name%2C%20a%20list%20of%20parameters%2C%20and%20a%20list%20of%20return%20values.%0A%0AHere's%20an%20example%20of%20an%20interface%20that%20defines%20a%20single%20method%20called%20Area%20that%20calculates%20the%20area%20of%20a%20shape%3A%0A%0A%60%60%60go%0Atype%20Shape%20interface%20%7B%0A%20%20Area()%20float64%0A%7D%0A%60%60%60%0A%0AWe%20can%20also%20define%20an%20interface%20with%20multiple%20methods%3A%0A%0A%60%60%60go%0Atype%20Shape%20interface%20%7B%0A%20%20Area()%20float64%0A%20%20Perimeter()%20float64%0A%7D%0A%60%60%60%0A%0A%23%23%20Implementing%20an%20interface%20in%20a%20struct%0A%0ATo%20implement%20an%20interface%20in%20a%20struct%2C%20we%20simply%20define%20the%20methods%20specified%20in%20the%20interface%20in%20the%20struct.%20The%20method%20signatures%20must%20match%20the%20ones%20in%20the%20interface%20exactly.%0A%0AHere's%20an%20example%20of%20a%20struct%20that%20implements%20the%20Shape%20interface%3A%0A%0A%60%60%60go%0Atype%20Rectangle%20struct%20%7B%0A%20%20Width%20%20float64%0A%20%20Height%20float64%0A%7D%0A%0Afunc%20(r%20Rectangle)%20Area()%20float64%20%7B%0A%20%20return%20r.Width%20*%20r.Height%0A%7D%0A%0Afunc%20(r%20Rectangle)%20Perimeter()%20float64%20%7B%0A%20%20return%202%20*%20(r.Width%20%2B%20r.Height)%0A%7D%0A%60%60%60%0A%0A%23%23%20Using%20an%20interface%0A%0ATo%20use%20an%20interface%20in%20Go%2C%20we%20simply%20define%20a%20variable%20with%20the%20interface%20type%20and%20assign%20a%20value%20of%20a%20struct%20that%20implements%20the%20interface%20to%20it.%0A%0A%60%60%60go%0Avar%20shape%20Shape%0Ashape%20%3D%20Rectangle%7B2.0%2C%203.0%7D%0A%60%60%60%0A%0AWe%20can%20then%20call%20the%20methods%20defined%20in%20the%20interface%20using%20the%20interface%20variable%3A%0A%0A%60%60%60go%0Aarea%20%3A%3D%20shape.Area()%0Afmt.Println(%22Area%3A%22%2C%20area)%20%20%2F%2F%20Output%3A%20Area%3A%206%0A%60%60%60%0A%0A%23%23%23%20Type%20assertions%20and%20type%20switches%0A%0ASometimes%20we%20need%20to%20determine%20the%20specific%20type%20of%20a%20value%20that%20satisfies%20an%20interface.%20We%20can%20do%20this%20using%20a%20type%20assertion%20or%20a%20type%20switch.%0A%0AA%20type%20assertion%20allows%20us%20to%20check%20if%20a%20value%20has%20a%20specific%20type%20and%20retrieve%20the%20value%20in%20that%20type.%20It%20has%20the%20form%20value.(Type)%2C%20where%20value%20is%20the%20interface%20value%20and%20Type%20is%20the%20type%20we%20want%20to%20assert%20the%20value%20is.%0A%0A%60%60%60go%0Aif%20rect%2C%20ok%20%3A%3D%20shape.(Rectangle)%3B%20ok%20%7B%0A%20%20fmt.Println(%22Width%3A%22%2C%20rect.Width)%0A%20%20fmt.Println(%22Height%3A%22%2C%20rect.Height)%0A%7D%20else%20%7B%0A%20%20fmt.Println(%22Not%20rectangle%22)%0A%7D%0A%60%60%60

Interface

Concurrency%20is%20an%20important%20aspect%20of%20programming%2C%20and%20it%20is%20especially%20useful%20in%20the%20field%20of%20network%20programming%2C%20where%20a%20single%20machine%20may%20have%20to%20handle%20multiple%20client%20requests%20simultaneously.%20Go%20is%20a%20programming%20language%20that%20was%20designed%20with%20concurrency%20in%20mind%2C%20and%20it%20offers%20a%20number%20of%20features%20that%20make%20it%20easy%20for%20developers%20to%20write%20concurrent%20code.%0A%0AOne%20of%20the%20key%20features%20of%20Go%20that%20enables%20concurrency%20is%20the%20goroutine%2C%20which%20is%20a%20lightweight%20thread%20of%20execution.%20Goroutines%20are%20very%20cheap%20to%20create%20and%20manage%2C%20and%20they%20can%20be%20created%20with%20the%20go%20keyword%20followed%20by%20a%20function%20call.%20For%20example%3A%0A%0A%60%60%60go%0Ago%20myFunction()%0A%60%60%60%0A%0AThis%20will%20create%20a%20new%20goroutine%20that%20will%20execute%20the%20myFunction%20function%20concurrently%20with%20the%20rest%20of%20the%20code.%0A%0AAnother%20key%20feature%20of%20Go%20that%20enables%20concurrency%20is%20the%20channel%2C%20which%20is%20a%20type%20of%20data%20structure%20that%20allows%20one%20goroutine%20to%20send%20data%20to%20another%20goroutine.%20Channels%20can%20be%20created%20using%20the%20make%20function%2C%20and%20they%20can%20be%20used%20to%20send%20and%20receive%20data%20using%20the%20%3C-%20operator.%20For%20example%3A%0A%0A%60%60%60go%0Ach%20%3A%3D%20make(chan%20int)%0Ago%20func()%20%7B%0A%20%20%20%20ch%20%3C-%201%0A%7D()%0Ax%20%3A%3D%20%3C-%20ch%0A%60%60%60%0A%0AIn%20this%20example%2C%20we%20create%20a%20channel%20of%20integers%2C%20and%20then%20we%20create%20a%20new%20goroutine%20that%20sends%20the%20value%201%20to%20the%20channel.%20The%20main%20goroutine%20then%20receives%20the%20value%20from%20the%20channel%20and%20stores%20it%20in%20the%20x%20variable.%0A%0AThere%20are%20many%20other%20features%20of%20Go%20that%20make%20it%20well-suited%20for%20concurrent%20programming%2C%20such%20as%20the%20sync%20package%2C%20which%20provides%20tools%20for%20synchronizing%20goroutines%2C%20and%20the%20select%20statement%2C%20which%20allows%20multiple%20goroutines%20to%20communicate%20with%20each%20other%20using%20channels.%0A%0AIn%20conclusion%2C%20Go%20is%20a%20powerful%20programming%20language%20that%20makes%20it%20easy%20for%20developers%20to%20write%20concurrent%20code.%20Its%20support%20for%20goroutines%20and%20channels%2C%20as%20well%20as%20other%20features%20such%20as%20the%20sync%20package%20and%20the%20select%20statement%2C%20make%20it%20an%20ideal%20choice%20for%20building%20high-performance%2C%20scalable%20applications.

Concurrency & Channel

Golang In-Depth

Building Scalable, High-Performance Go Web Applications

%5C%0A**Java**%20is%20one%20of%20the%20most%20popular%20programming%20language%20in%20the%20world.%20Java%20first%20appeared%2027%20years%20ago%20and%20was%20designed%20by%20James%20Gosling.%0A%0A%5C%0AJava%20is%20a%20high%20level%2C%20object%20oriented%20programming%20language.%20In%20this%20course%20you%20will%20learn%20the%20fundamentals%20of%20Java%20programming%20language.%20After%20completing%20this%20course%2C%20I%20hope%20you%20will%20have%20a%20solid%20understanding%20of%20Java%20eco-system.%20Along%20with%20Java%20fundamentals%20I%20will%20also%20try%20to%20cover%20some%20topics%20from%20latest%20Java%20versions%20such%20as%20Stream%20API%2C%20New%20IO%20API%20etc.%0A%0A%5C%0A**Language**%3A%20English%0A%0A%5C%0A**Level**%3A%20Intermediate%0A%0A%5C%0A**Content%20Format**%3A%20Text%0A%0A%5C%0A**Note%3A%20Use%20nagivation%20bar%20to%20browse%20course%20materials.**

%60%60%60java%0Apublic%20class%20LearnYouSomeJavaForGreatGood%20%7B%0A%0A%20%20%20%20public%20static%20void%20main(String%5B%5D%20args)%20%7B%0A%20%20%20%20%20%20%20%20System.out.println(%22Hello%20World%22)%3B%0A%20%20%20%20%7D%0A%7D%0A%60%60%60

%23%23%23%20Data%20Types%20in%20Java%0A%0AA%20data%20type%20is%20a%20classification%20that%20specifies%20the%20kind%20of%20value%20that%20a%20variable%20can%20hold.%20In%20Java%2C%20there%20are%20two%20types%20of%20data%3A%20primitive%20and%20reference.%0A%0A%23%23%23%23%20Primitive%20Data%20Types%0A%0APrimitive%20data%20types%20are%20the%20basic%20data%20types%20that%20are%20built%20into%20the%20Java%20language.%20They%20include%3A%0A%0A*%20boolean%3A%20a%20value%20that%20is%20either%20true%20or%20false%0A*%20char%3A%20a%20single%20character%0A*%20byte%3A%20an%208-bit%20integer%0A*%20short%3A%20a%2016-bit%20integer%0A*%20int%3A%20a%2032-bit%20integer%0A*%20long%3A%20a%2064-bit%20integer%0A*%20float%3A%20a%2032-bit%20floating%20point%20number%0A*%20double%3A%20a%2064-bit%20floating%20point%20number%0A%0APrimitive%20data%20types%20are%20stored%20directly%20in%20the%20memory%20and%20are%20generally%20more%20efficient%20than%20reference%20data%20types.%20However%2C%20they%20are%20limited%20in%20the%20kind%20of%20information%20they%20can%20represent.%0A%0A%23%23%23%23%20Reference%20Data%20Types%0A%0AReference%20data%20types%20are%20variables%20that%20hold%20a%20reference%20(i.e.%2C%20an%20address)%20to%20an%20object%20in%20memory.%20This%20means%20that%20when%20you%20create%20an%20object%20in%20Java%2C%20you%20are%20actually%20creating%20a%20reference%20to%20the%20object.%0A%0ASome%20examples%20of%20reference%20data%20types%20in%20Java%20include%3A%0A%0A*%20String%3A%20a%20sequence%20of%20characters%0A*%20Array%3A%20an%20ordered%20collection%20of%20elements%0A*%20Classes%3A%20a%20template%20for%20creating%20objects%0A%0AReference%20data%20types%20are%20more%20flexible%20than%20primitive%20data%20types%20because%20they%20can%20represent%20a%20wide%20variety%20of%20information.%20However%2C%20they%20are%20less%20efficient%20because%20they%20require%20additional%20memory%20to%20store%20the%20reference%20to%20the%20object.%0A%0A%23%23%23%20Objects%20in%20Java%0A%0AAn%20object%20is%20a%20self-contained%20unit%20that%20consists%20of%20both%20data%20and%20behavior.%20In%20Java%2C%20objects%20are%20created%20from%20classes%2C%20which%20act%20as%20a%20template%20for%20creating%20objects.%0A%0ATo%20create%20an%20object%20in%20Java%2C%20you%20first%20need%20to%20define%20a%20class.%20A%20class%20is%20a%20blueprint%20that%20defines%20the%20properties%20and%20methods%20of%20an%20object.%20Here%20is%20an%20example%20of%20a%20simple%20class%20in%20Java%3A%0A%0A%60%60%60java%0Apublic%20class%20Person%20%7B%0A%20%20%2F%2F%20properties%0A%20%20private%20String%20name%3B%0A%20%20private%20int%20age%3B%0A%20%20%0A%20%20%2F%2F%20methods%0A%20%20public%20void%20setName(String%20name)%20%7B%0A%20%20%20%20this.name%20%3D%20name%3B%0A%20%20%7D%0A%20%20%0A%20%20public%20String%20getName()%20%7B%0A%20%20%20%20return%20this.name%3B%0A%20%20%7D%0A%20%20%0A%20%20public%20void%20setAge(int%20age)%20%7B%0A%20%20%20%20this.age%20%3D%20age%3B%0A%20%20%7D%0A%20%20%0A%20%20public%20int%20getAge()%20%7B%0A%20%20%20%20return%20this.age%3B%0A%20%20%7D%0A%7D%0A%60%60%60%0A%0ATo%20create%20an%20object%20from%20this%20class%2C%20you%20would%20use%20the%20%60new%60%20keyword%2C%20like%20this%3A%0A%0A%60%60%60java%0APerson%20person%20%3D%20new%20Person()%3B%0A%60%60%60%0A%0AThis%20creates%20an%20instance%20of%20the%20Person%20class%20and%20assigns%20it%20to%20the%20person%20variable.%20You%20can%20then%20use%20the%20methods%20of%20the%20Person%20class%20to%20set%20and%20get%20the%20values%20of%20the%20object's%20properties.%20For%20example%3A%0A%0A%60%60%60java%0Aperson.setName(%22John%22)%3B%0Aperson.setAge(30)%3B%0A%0ASystem.out.println(person.getName())%3B%20%2F%2F%20prints%20%22John%22%0ASystem.out.println(person.getAge())%3B%20%2F%2F%20prints%2030%0A%60%60%60

Data Types & Objects

%23%23%23%20Conditionals%20in%20Java%0A%0AConditionals%20are%20statements%20that%20allow%20you%20to%20execute%20different%20blocks%20of%20code%20based%20on%20whether%20a%20particular%20condition%20is%20true%20or%20false.%20In%20Java%2C%20you%20can%20use%20the%20if%20statement%20to%20execute%20a%20block%20of%20code%20if%20a%20condition%20is%20true%2C%20and%20the%20if-else%20statement%20to%20execute%20a%20block%20of%20code%20if%20the%20condition%20is%20true%20or%20another%20block%20of%20code%20if%20the%20condition%20is%20false.%0A%0AHere%20is%20an%20example%20of%20an%20if%20statement%20in%20Java%3A%0A%0A%60%60%60java%0Aint%20x%20%3D%2010%3B%0Aif%20(x%20%3E%205)%20%7B%0A%20%20System.out.println(%22x%20is%20greater%20than%205%22)%3B%0A%7D%0A%60%60%60%0A%0AThis%20code%20will%20print%20%22x%20is%20greater%20than%205%22%20because%20the%20condition%20x%20%3E%205%20is%20true.%0A%0AHere%20is%20an%20example%20of%20an%20if-else%20statement%20in%20Java%3A%0A%0A%60%60%60java%0Aint%20y%20%3D%203%3B%0Aif%20(y%20%3E%205)%20%7B%0A%20%20System.out.println(%22y%20is%20greater%20than%205%22)%3B%0A%7D%20else%20%7B%0A%20%20System.out.println(%22y%20is%20not%20greater%20than%205%22)%3B%0A%7D%0A%60%60%60%0A%0AThis%20code%20will%20print%20%22y%20is%20not%20greater%20than%205%22%20because%20the%20condition%20y%20%3E%205%20is%20false.%0A%0AIn%20addition%20to%20the%20if%20and%20if-else%20statements%2C%20Java%20also%20provides%20the%20switch%20statement%2C%20which%20allows%20you%20to%20execute%20different%20blocks%20of%20code%20based%20on%20the%20value%20of%20a%20variable.%20Here%20is%20an%20example%20of%20a%20switch%20statement%20in%20Java%3A%0A%0A%60%60%60java%0Aint%20z%20%3D%202%3B%0Aswitch%20(z)%20%7B%0A%20%20case%201%3A%0A%20%20%20%20System.out.println(%22z%20is%201%22)%3B%0A%20%20%20%20break%3B%0A%20%20case%202%3A%0A%20%20%20%20System.out.println(%22z%20is%202%22)%3B%0A%20%20%20%20break%3B%0A%20%20case%203%3A%0A%20%20%20%20System.out.println(%22z%20is%203%22)%3B%0A%20%20%20%20break%3B%0A%20%20default%3A%0A%20%20%20%20System.out.println(%22z%20is%20not%201%2C%202%2C%20or%203%22)%3B%0A%7D%0A%60%60%60%0A%0AThis%20code%20will%20print%20%22z%20is%202%22%20because%20the%20value%20of%20z%20is%202.%0A%0A%23%23%23%20Loops%20in%20Java%0A%0ALoops%20are%20statements%20that%20allow%20you%20to%20execute%20a%20block%20of%20code%20repeatedly%20until%20a%20certain%20condition%20is%20met.%20In%20Java%2C%20there%20are%20three%20types%20of%20loops%3A%20the%20for%20loop%2C%20the%20while%20loop%2C%20and%20the%20do-while%20loop.%0A%0A**The%20for%20Loop**%0AThe%20for%20loop%20is%20used%20to%20execute%20a%20block%20of%20code%20a%20specific%20number%20of%20times.%20Here%20is%20an%20example%20of%20a%20for%20loop%20in%20Java%3A%0A%0A%60%60%60java%0Afor%20(int%20i%20%3D%200%3B%20i%20%3C%205%3B%20i%2B%2B)%20%7B%0A%20%20System.out.println(%22Hello%2C%20World!%22)%3B%0A%7D%0A%60%60%60%0A%0AThis%20code%20will%20print%20%22Hello%2C%20World!%22%20five%20times.%20The%20loop%20initializes%20a%20variable%20i%20to%200%2C%20then%20checks%20if%20i%20is%20less%20than%205.%20If%20it%20is%2C%20it%20executes%20the%20block%20of%20code%20and%20increments%20i%20by%201.%20If%20i%20is%20not%20less%20than%205%2C%20the%20loop%20ends.%0A%0A**The%20while%20Loop**%0AThe%20while%20loop%20is%20used%20to%20execute%20a%20block%20of%20code%20as%20long%20as%20a%20certain%20condition%20is%20true.%20Here%20is%20an%20example%20of%20a%20while%20loop%20in%20Java%3A%0A%0A%60%60%60java%0Aint%20j%20%3D%200%3B%0Awhile%20(j%20%3C%205)%20%7B%0A%20%20System.out.println%0A%7D%0A%60%60%60

Java%20methods%20are%20an%20essential%20concept%20in%20Java%20programming.%20A%20method%20is%20a%20block%20of%20code%20that%20performs%20a%20specific%20task%20and%20can%20be%20called%20from%20anywhere%20in%20a%20program.%20In%20this%20blog%20post%2C%20we%20will%20explore%20methods%20in%20more%20detail%20and%20see%20how%20they%20are%20used%20in%20Java%20programming.%0A%0A%23%23%23%20What%20are%20Java%20Methods%3F%0A%0AJava%20methods%20are%20a%20way%20to%20encapsulate%20a%20block%20of%20code%20and%20give%20it%20a%20name.%20This%20makes%20it%20easier%20to%20reuse%20the%20code%20in%20different%20parts%20of%20a%20program%20and%20makes%20the%20code%20more%20organized%20and%20maintainable.%0A%0AA%20method%20has%20a%20signature%20and%20a%20body.%20The%20signature%20consists%20of%20the%20name%20of%20the%20method%2C%20the%20return%20type%2C%20and%20the%20parameters.%20The%20body%20consists%20of%20the%20code%20that%20is%20executed%20when%20the%20method%20is%20called.%0A%0AHere%20is%20an%20example%20of%20a%20simple%20method%20in%20Java%3A%0A%0A%60%60%60java%0Apublic%20static%20void%20sayHello()%20%7B%0A%20%20System.out.println(%22Hello%2C%20World!%22)%3B%0A%7D%0A%60%60%60%0A%0AThis%20method%20has%20the%20name%20sayHello%2C%20a%20return%20type%20of%20void%2C%20and%20no%20parameters.%20The%20body%20of%20the%20method%20consists%20of%20a%20single%20line%20of%20code%20that%20prints%20%22Hello%2C%20World!%22%20to%20the%20console.%0A%0A%23%23%23%23%20How%20to%20Call%20a%20Java%20Method%0A%0ATo%20call%20a%20method%20in%20Java%2C%20you%20simply%20use%20the%20name%20of%20the%20method%20followed%20by%20parentheses.%20For%20example%3A%0A%0A%60%60%60java%0AsayHello()%3B%0A%60%60%60%0A%0AThis%20will%20execute%20the%20code%20in%20the%20body%20of%20the%20sayHello%20method%20and%20print%20%22Hello%2C%20World!%22%20to%20the%20console.%0A%0A%23%23%23%23%20Method%20Parameters%20and%20Return%20Values%0A%0AJava%20methods%20can%20have%20parameters%2C%20which%20are%20variables%20that%20are%20passed%20to%20the%20method%20when%20it%20is%20called.%20The%20method%20can%20use%20the%20parameters%20to%20perform%20its%20task%20and%20optionally%20return%20a%20value%20to%20the%20caller.%0A%0AHere%20is%20an%20example%20of%20a%20method%20with%20parameters%20and%20a%20return%20value%3A%0A%0A%60%60%60java%0Apublic%20static%20int%20add(int%20x%2C%20int%20y)%20%7B%0A%20%20return%20x%20%2B%20y%3B%0A%7D%0A%60%60%60%0A%0AThis%20method%20has%20the%20name%20add%2C%20a%20return%20type%20of%20int%2C%20and%20two%20parameters%3A%20x%20and%20y.%20The%20body%20of%20the%20method%20consists%20of%20a%20single%20line%20of%20code%20that%20adds%20the%20values%20of%20x%20and%20y%20and%20returns%20the%20result.%0A%0ATo%20call%20this%20method%2C%20you%20would%20pass%20it%20two%20integers%20as%20arguments%3A%0A%0A%60%60%60java%0Aint%20sum%20%3D%20add(3%2C%204)%3B%0A%60%60%60%0A%0AThis%20would%20assign%20the%20value%207%20to%20the%20variable%20sum.%0A%0AJava%20methods%20are%20a%20powerful%20tool%20that%20allow%20you%20to%20encapsulate%20and%20reuse%20code%20in%20your%20programs.%20They%20make%20it%20easier%20to%20organize%20and%20maintain%20your%20code%2C%20and%20they%20allow%20you%20to%20define%20precise%20interfaces%20for%20interacting%20with%20your%20code.%20By%20using%20methods%20effectively%2C%20you%20can%20write%20more%20efficient%20and%20maintainable%20Java%20programs.

Methods / Functions

Java Basics

%23%23%23%20Java%20Array%0A%0AAn%20array%20is%20a%20collection%20of%20elements%20that%20are%20stored%20in%20a%20contiguous%20block%20of%20memory.%20In%20Java%2C%20an%20array%20is%20an%20object%20that%20holds%20a%20fixed%20number%20of%20values%20of%20the%20same%20data%20type.%0A%0ATo%20create%20an%20array%20in%20Java%2C%20you%20use%20the%20new%20keyword%20followed%20by%20the%20data%20type%20of%20the%20elements%20and%20the%20size%20of%20the%20array.%20Here%20is%20an%20example%20of%20how%20to%20create%20an%20array%20of%20integers%20in%20Java%3A%0A%0A%60%60%60java%0Aint%5B%5D%20numbers%20%3D%20new%20int%5B5%5D%3B%0A%60%60%60%0A%0AThis%20creates%20an%20array%20of%20integers%20with%20a%20size%20of%205.%20You%20can%20also%20initialize%20the%20array%20with%20values%20like%20this%3A%0A%0A%60%60%60java%0Aint%5B%5D%20numbers%20%3D%20%7B1%2C%202%2C%203%2C%204%2C%205%7D%3B%0A%60%60%60%0A%0ATo%20access%20an%20element%20of%20an%20array%2C%20you%20use%20the%20index%20of%20the%20element%20in%20square%20brackets.%20For%20example%3A%0A%0A%60%60%60java%0Aint%20firstElement%20%3D%20numbers%5B0%5D%3B%0Aint%20secondElement%20%3D%20numbers%5B1%5D%3B%0A%60%60%60%0A%0AYou%20can%20also%20use%20a%20loop%20to%20iterate%20over%20all%20the%20elements%20of%20an%20array%3A%0A%0A%60%60%60java%0Afor%20(int%20i%20%3D%200%3B%20i%20%3C%20numbers.length%3B%20i%2B%2B)%20%7B%0A%20%20int%20element%20%3D%20numbers%5Bi%5D%3B%0A%20%20System.out.println(element)%3B%0A%7D%0A%60%60%60%0A%0A%23%23%23%20Java%20List%0A%0AA%20list%20is%20a%20collection%20of%20elements%20that%20can%20grow%20or%20shrink%20dynamically.%20In%20Java%2C%20a%20list%20is%20an%20interface%20that%20represents%20an%20ordered%20collection%20of%20elements.%20There%20are%20several%20implementations%20of%20the%20List%20interface%2C%20including%20ArrayList%20and%20LinkedList.%0A%0ATo%20create%20a%20list%20in%20Java%2C%20you%20use%20the%20new%20keyword%20followed%20by%20the%20class%20that%20implements%20the%20List%20interface.%20Here%20is%20an%20example%20of%20how%20to%20create%20an%20ArrayList%20in%20Java%3A%0A%0A%60%60%60java%0AList%3CString%3E%20names%20%3D%20new%20ArrayList%3C%3E()%3B%0A%60%60%60%0A%0AThis%20creates%20an%20empty%20ArrayList%20of%20strings.%20You%20can%20also%20initialize%20the%20list%20with%20values%20like%20this%3A%0A%0A%60%60%60java%0AList%3CString%3E%20names%20%3D%20new%20ArrayList%3C%3E(Arrays.asList(%22Alice%22%2C%20%22Bob%22%2C%20%22Charlie%22))%3B%0A%60%60%60%0A%0ATo%20add%20an%20element%20to%20a%20list%2C%20you%20use%20the%20add%20method%3A%0A%0A%60%60%60java%0Anames.add(%22Dave%22)%3B%0A%60%60%60%0A%0ATo%20remove%20an%20element%20from%20a%20list%2C%20you%20use%20the%20remove%20method%3A%0A%0A%60%60%60java%0Anames.remove(%22Bob%22)%3B%0A%60%60%60%0A%0ATo%20access%20an%20element%20of%20a%20list%2C%20you%20use%20the%20get%20method%20and%20pass%20it%20the%20index%20of%20the%20element%3A%0A%0A%60%60%60java%0AString%20firstElement%20%3D%20names.get(0)%3B%0AString%20secondElement%20%3D%20names.get(1)%3B%0A%60%60%60%0A%0AYou%20can%20also%20use%20a%20loop%20to%20iterate%20over%20all%20the%20elements%20of%20a%20list%3A%0A%0A%60%60%60java%0Afor%20(String%20name%20%3A%20names)%20%7B%0A%20%20System.out.println(name)%3B%0A%7D%0A%60%60%60%0A%0AIn%20this%20lesson%2C%20we%20learned%20about%20arrays%20and%20lists%20in%20Java.%20Arrays%20are%20fixed-size%20collections%20of%20elements%2C%20while%20lists%20are%20dynamic%20collections%20of%20elements.%20Both%20are%20useful%20for%20storing%20and%20manipulating%20data%20in%20Java%20programs.

Array & List

%23%23%23%20Java%20Map%0A%0AA%20map%20is%20a%20collection%20of%20key-value%20pairs.%20In%20Java%2C%20a%20map%20is%20an%20interface%20that%20represents%20a%20mapping%20of%20keys%20to%20values.%20There%20are%20several%20implementations%20of%20the%20Map%20interface%2C%20including%20HashMap%20and%20TreeMap.%0A%0ATo%20create%20a%20map%20in%20Java%2C%20you%20use%20the%20new%20keyword%20followed%20by%20the%20class%20that%20implements%20the%20Map%20interface.%20Here%20is%20an%20example%20of%20how%20to%20create%20a%20HashMap%20in%20Java%3A%0A%0A%60%60%60java%0AMap%3CString%2C%20Integer%3E%20grades%20%3D%20new%20HashMap%3C%3E()%3B%0A%60%60%60%0A%0AThis%20creates%20an%20empty%20HashMap%20that%20maps%20strings%20(the%20keys)%20to%20integers%20(the%20values).%0A%0ATo%20add%20a%20key-value%20pair%20to%20a%20map%2C%20you%20use%20the%20put%20method%3A%0A%0A%60%60%60java%0Agrades.put(%22Alice%22%2C%2090)%3B%0Agrades.put(%22Bob%22%2C%2080)%3B%0A%60%60%60%0A%0ATo%20get%20the%20value%20for%20a%20particular%20key%2C%20you%20use%20the%20get%20method%3A%0A%0A%60%60%60java%0Aint%20aliceGrade%20%3D%20grades.get(%22Alice%22)%3B%0Aint%20bobGrade%20%3D%20grades.get(%22Bob%22)%3B%0A%60%60%60%0A%0ATo%20remove%20a%20key-value%20pair%20from%20a%20map%2C%20you%20use%20the%20remove%20method%3A%0A%0A%60%60%60java%0Agrades.remove(%22Bob%22)%3B%0A%60%60%60%0A%0AYou%20can%20also%20use%20the%20keySet%20method%20to%20get%20a%20set%20of%20all%20the%20keys%20in%20the%20map%3A%0A%0A%60%60%60java%0ASet%3CString%3E%20keys%20%3D%20grades.keySet()%3B%0A%60%60%60

%23%23%23%20Java%20Set%0A%0AA%20set%20is%20a%20collection%20of%20unique%20elements.%20In%20Java%2C%20a%20set%20is%20an%20interface%20that%20represents%20a%20collection%20of%20elements%20that%20does%20not%20allow%20duplicate%20values.%20There%20are%20several%20implementations%20of%20the%20Set%20interface%2C%20including%20HashSet%20and%20TreeSet.%0A%0ATo%20create%20a%20set%20in%20Java%2C%20you%20use%20the%20new%20keyword%20followed%20by%20the%20class%20that%20implements%20the%20Set%20interface.%20Here%20is%20an%20example%20of%20how%20to%20create%20a%20HashSet%20in%20Java%3A%0A%0A%60%60%60java%0ASet%3CString%3E%20names%20%3D%20new%20HashSet%3C%3E()%3B%0A%60%60%60%0A%0AThis%20creates%20an%20empty%20HashSet%20of%20strings.%0A%0ATo%20add%20an%20element%20to%20a%20set%2C%20you%20use%20the%20add%20method%3A%0A%0A%60%60%60java%0Anames.add(%22Alice%22)%3B%0Anames.add(%22Bob%22)%3B%0A%60%60%60%0A%0ATo%20check%20if%20an%20element%20is%20in%20a%20set%2C%20you%20use%20the%20contains%20method%3A%0A%0A%60%60%60java%0Aif%20(names.contains(%22Alice%22))%20%7B%0A%20%20System.out.println(%22Alice%20is%20in%20the%20set.%22)%3B%0A%7D%0A%60%60%60%0A%0ATo%20remove%20an%20element%20from%20a%20set%2C%20you%20use%20the%20remove%20method%3A%0A%0A%60%60%60java%0Anames.remove(%22Bob%22)%3B%0A%60%60%60%0A%0AYou%20can%20also%20use%20a%20loop%20to%20iterate%20over%20all%20the%20elements%20of%20a%20set%3A%0A%0A%60%60%60java%0Afor%20(String%20name%20%3A%20names)%20%7B%0A%20%20System.out.println(name)%3B%0A%7D%0A%60%60%60

Collection Framework

In%20this%20lesson%2C%20we%20will%20learn%20about%20two%20important%20concepts%20in%20Java%3A%20classes%20and%20inheritance.%0A%0A%23%23%23%20Java%20Class%0A%0AA%20class%20is%20a%20template%20for%20creating%20objects.%20In%20Java%2C%20a%20class%20is%20a%20blueprint%20that%20defines%20the%20properties%20and%20methods%20of%20an%20object.%20A%20class%20has%20three%20parts%3A%0A%0A*%20Fields%3A%20variables%20that%20hold%20the%20state%20of%20an%20object%0A*%20Methods%3A%20functions%20that%20define%20the%20behavior%20of%20an%20object%0A*%20Constructors%3A%20special%20methods%20that%20are%20called%20when%20an%20object%20is%20created%0A%0AHere%20is%20an%20example%20of%20a%20simple%20class%20in%20Java%3A%0A%0A%60%60%60java%0Apublic%20class%20Person%20%7B%0A%20%20%2F%2F%20fields%0A%20%20private%20String%20name%3B%0A%20%20private%20int%20age%3B%0A%0A%20%20%2F%2F%20methods%0A%20%20public%20void%20setName(String%20name)%20%7B%0A%20%20%20%20this.name%20%3D%20name%3B%0A%20%20%7D%0A%0A%20%20public%20String%20getName()%20%7B%0A%20%20%20%20return%20this.name%3B%0A%20%20%7D%0A%0A%20%20public%20void%20setAge(int%20age)%20%7B%0A%20%20%20%20this.age%20%3D%20age%3B%0A%20%20%7D%0A%0A%20%20public%20int%20getAge()%20%7B%0A%20%20%20%20return%20this.age%3B%0A%20%20%7D%0A%7D%0A%60%60%60%0A%0AThis%20class%20has%20two%20fields%3A%20name%20and%20age.%20It%20has%20four%20methods%3A%20setName%2C%20getName%2C%20setAge%2C%20and%20getAge.%20These%20methods%20allow%20you%20to%20set%20and%20get%20the%20values%20of%20the%20name%20and%20age%20fields.%0A%0ATo%20create%20an%20object%20from%20a%20class%2C%20you%20use%20the%20new%20keyword%20followed%20by%20the%20class%20name%20and%20constructor%20arguments%3A%0A%0A%60%60%60java%0APerson%20person%20%3D%20new%20Person()%3B%0A%60%60%60%0A%0AThis%20creates%20an%20instance%20of%20the%20Person%20class%20and%20assigns%20it%20to%20the%20person%20variable.%20You%20can%20then%20use%20the%20methods%20of%20the%20Person%20class%20to%20set%20and%20get%20the%20values%20of%20the%20object's%20fields%3A%0A%0A%60%60%60java%0Aperson.setName(%22Alice%22)%3B%0A%60%60%60%0A%0A%23%23%23%20What%20is%20Inheritance%3F%0A%0AInheritance%20is%20a%20mechanism%20that%20allows%20you%20to%20create%20a%20new%20class%20that%20is%20a%20modified%20version%20of%20an%20existing%20class.%20The%20new%20class%20is%20called%20the%20subclass%2C%20and%20the%20existing%20class%20is%20the%20superclass.%20The%20subclass%20inherits%20the%20properties%20and%20methods%20of%20the%20superclass%20and%20can%20also%20have%20its%20own%20properties%20and%20methods.%0A%0AHere%20is%20an%20example%20of%20inheritance%20in%20Java%3A%0A%0A%60%60%60java%0Apublic%20class%20Animal%20%7B%0A%20%20%2F%2F%20fields%0A%20%20protected%20String%20name%3B%0A%0A%20%20%2F%2F%20methods%0A%20%20public%20void%20setName(String%20name)%20%7B%0A%20%20%20%20this.name%20%3D%20name%3B%0A%20%20%7D%0A%0A%20%20public%20String%20getName()%20%7B%0A%20%20%20%20return%20this.name%3B%0A%20%20%7D%0A%7D%0A%0Apublic%20class%20Dog%20extends%20Animal%20%7B%0A%20%20%2F%2F%20fields%0A%20%20private%20String%20breed%3B%0A%0A%20%20%2F%2F%20methods%0A%20%20public%20void%20setBreed(String%20breed)%20%7B%0A%20%20%20%20this.breed%20%3D%20breed%3B%0A%20%20%7D%0A%0A%20%20public%20String%20getBreed()%20%7B%0A%20%20%20%20return%20this.breed%3B%0A%20%20%7D%0A%7D%0A%60%60%60%0A%0AIn%20this%20example%2C%20the%20Animal%20class%20is%20the%20superclass%20and%20the%20Dog%20class%20is%20the%20subclass.%20The%20Dog%20class%20inherits%20the%20name%20field%20and%20the%20setName%20and%20getName%20methods%20from%20the%20Animal%20class.%20It%20also%20has%20its%20own%20breed%20field%20and%20setBreed%20and%20getBreed%20methods.%0A%0ATo%20create%20an%20object%20of%20the%20Dog%20class%2C%20you%20use%20the%20new%20keyword%20and%20the%20constructor%20arguments%3A%0A%0A%60%60%60java%0ADog%20dog%20%3D%20new%20Dog()%3B%0A%60%60%60%0A%0AYou%20can%20then%20use%20the%20inherited%20and%20custom%20methods%20of%20the%20Dog%20class%20to%20set%20and%20get%20the%20values%20of%20the%20object's%20fields%3A%0A%0A%60%60%60java%0Adog.setName(%22Buddy%22)%3B%0Adog.setBreed(%22Labrador%22)%3B%0A%60%60%60%0A%0A%23%23%23%23%20Why%20Use%20Inheritance%3F%0A%0AThere%20are%20several%20reasons%20to%20use%20inheritance%20in%20Java%3A%0A%0A*%20Code%20reuse%3A%20You%20can%20reuse%20the%20code%20from%20the%20superclass%20in%20the%20subclass%2C%20which%20saves%20time%20and%20reduces%20the%20risk%20of%20errors.%0A*%20Polymorphism%3A%20You%20can%20use%20a%20subclass%20object%20in%20the%20same%20way%20as%20a%20superclass%20object%2C%20which%20allows%20you%20to%20write%20more%20flexible%20and%20reusable%20code.%0A*%20Simplicity%3A%20You%20can%20create%20a%20subclass%20that%20only%20includes%20the%20modifications%20you%20need%2C%20which%20makes%20your%20code%20simpler%20and%20easier%20to%20understand.%0A%0AInheritance%20is%20a%20way%20to%20create%20a%20new%20class%20that%20is%20a%20modified%20version%20of%20an%20existing%20class.%20It%20allows%20you%20to%20reuse%20code%2C%20write%20more%20flexible%20and%20reusable%20code%2C%20and%20create%20simpler%20and%20easier%20to%20understand%20classes.

Class & Inheritance

Abstraction

Polymorphism

Encapsulation

Java OOP

%23%23%23%20What%20is%20Interface%3F%0A%0AAn%20interface%20is%20a%20collection%20of%20abstract%20methods%2C%20which%20are%20methods%20that%20do%20not%20have%20an%20implementation.%20An%20interface%20specifies%20what%20an%20implementing%20class%20should%20do%2C%20but%20not%20how%20it%20should%20do%20it.%20Here%20is%20an%20example%20of%20an%20interface%20in%20Java%3A%0A%0A%60%60%60java%0Apublic%20interface%20Shape%20%7B%0A%20%20double%20getArea()%3B%0A%20%20double%20getPerimeter()%3B%0A%7D%0A%60%60%60%0A%0AThis%20interface%20has%20two%20abstract%20methods%3A%20getArea%20and%20getPerimeter.%20An%20implementing%20class%20must%20provide%20an%20implementation%20for%20these%20methods.%0A%0ATo%20implement%20an%20interface%2C%20a%20class%20must%20use%20the%20implements%20keyword%20and%20the%20name%20of%20the%20interface%3A%0A%0A%60%60%60java%0Apublic%20class%20Circle%20implements%20Shape%20%7B%0A%20%20%2F%2F%20fields%0A%20%20private%20double%20radius%3B%0A%0A%20%20%2F%2F%20methods%0A%20%20%40Override%0A%20%20public%20double%20getArea()%20%7B%0A%20%20%20%20return%20Math.PI%20*%20radius%20*%20radius%3B%0A%20%20%7D%0A%0A%20%20%40Override%0A%20%20public%20double%20getPerimeter()%20%7B%0A%20%20%20%20return%202%20*%20Math.PI%20*%20radius%3B%0A%20%20%7D%0A%0A%20%20%2F%2F%20constructor%0A%20%20public%20Circle(double%20radius)%20%7B%0A%20%20%20%20this.radius%20%3D%20radius%3B%0A%20%20%7D%0A%7D%0A%60%60%60%0A%0AIn%20this%20example%2C%20the%20Circle%20class%20implements%20the%20Shape%20interface%20and%20provides%20an%20implementation%20for%20the%20getArea%20and%20getPerimeter%20methods.%20The%20%40Override%20annotation%20is%20used%20to%20specify%20that%20the%20method%20is%20an%20implementation%20of%20an%20abstract%20method%20from%20the%20interface.%0A%0ATo%20use%20an%20interface%2C%20you%20can%20create%20a%20reference%20variable%20of%20the%20interface%20type%20and%20assign%20it%20an%20object%20of%20a%20class%20that%20implements%20the%20interface%3A%0A%0A%60%60%60java%0AShape%20circle%20%3D%20new%20Circle(5)%3B%0A%60%60%60%0A%0AThis%20creates%20an%20instance%20of%20the%20Circle%20class%20and%20assigns%20it%20to%20the%20circle%20variable%2C%20which%20is%20a%20reference%20to%20the%20Shape%20interface.%20You%20can%20then%20use%20the%20circle%20reference%20to%20call%20the%20%60getArea%60%20and%20%60getPerimeter%60.

Singleton Pattern

Dependency Injection

Java OOP Extended

Java File & IO

Java Network IO

Java IO

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