Go language Preliminary understanding

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//myNote1 project Main.go PackageMaindifferent packages are available in the//go language, equivalent to different classes in Java to provide functionalityImport("FMT")var(//This factorization keyword is commonly used to declare global variablesAaintBbBOOL)funcMain () {//Output statementFmt. Println ("Hello world!")//define Variables    varIinti =Ten    varj ="JJJJJJJJJJJJ"K: ="KKKKKKKKKKK"Fmt. Println ("Variable:", i) fmt. Println ("Variable:", j) Fmt. Println ("Variable:"K//define multiple variables    varS, u, gintS, u, g =Ten, -, -Fmt. Println ("Variable:", s) fmt. Println ("Variable:", u) fmt. Println ("Variable:", g)varA, b, C ="AAA","BBB","CCC"Fmt. Println ("Variable:", a) fmt. Println ("Variable:", b) fmt. Println ("Variable:", c) d, E, f: ="DDD","Eee","FFF"Fmt. Println ("Variable:", d) fmt. Println ("Variable:", e) fmt. Println ("Variable:", f)//global variableFmt. Println ("global variable:", AA) FMT. Println ("global variable:", BB)//Get the memory address of the variableFmt. Println ("Memory address:", &a)//When a variable is declared, but it is not used, it will be reported to JJ declared and not used    //var JJ string = "JK"    //Define constants programming habits are defined in uppercase letters .    //const defining constants of a specific type    ConstLeftint= -    Constright = $    ConstUp, down = -, -    Const(before = -after = -) FMT. Println ("constant:", left, right, up, down, before, after)//Operations    varV, Zint=Ten, -Fmt. Println ("Addition:", V+z) fmt. Println ("Subtraction:", V-z) fmt. Println ("Multiplication:", V*z) fmt. Println ("Division:", v/z) fmt. Println ("Take the remainder:", V%z) fmt. Println ("Less than equals:", v <= z) fmt. Println ("Equals:", v = = z)//if Else ElseIf    ifTen==Ten{FMT. Println ("if statement")    }ifTen== -{FMT. Println ("if statement")    }Else{FMT. Println ("Else Statement")    }//switchJK: ="a"    SwitchJK { Case "a": FMT. Println ("Branch Statement") Break     Case "B": FMT. Println ("xxxxx") Break    default: FMT. Println ("--------") Break}varindex =1     forIndex <4{FMT. Println ("-------") index++}varFlatint=3A:index =1     forIndex <3{FMT. Println ("xxxx") index++} flat++ifFlat <5{GotoA} testFun1 () testFun2(Ten, -) FMT. Println ("function returns:", TESTFUN3(Ten, -)) x, y: = TestFun4(Ten, -) FMT. Println ("function returns multiple values:", X, y)varArr[3]intArr[0] =1Arr[1] =TenArr[2] = +{varOpint=0         forOp <Len(arr) {FMT. Println (Arr[op]) op++}}//Do not set the size of the array    varARR1 = [...]float64{12.12,34.2,45.2} FMT. Println (ARR1)varARR2 =[5]float32{11.23,343.23,34.5} FMT. Println (ARR2)//Data structure pointers    varInchint= -Fmt. Println ("Address of the variable", &in)//Defines a pointer to an integer    varINI *intINI = &in FMT. Println ("pointer fetch data", *ini)//null pointer    varInk *intFmt. Println ("Judging null pointer", (Ink = =Nil))The //array can store the same type of data, but in structs we can define different data types for different items. Plainly, a class in Java that creates a template for an object.    typeBookstruct{TitlestringNumintnames []float32FlagBOOL}varBook1 Book Book1.flag =trueBook1.num =TenBook1.title ="Cao"Book1.names = []float32{1000.0,2.0,3.4,7.0,50.0} FMT. Println (Book1)The length of the//go array is immutable, and in a particular scenario such a collection is less applicable, and Go provides a flexible,    //powerful built-in type slicing ("Dynamic array"), the length of slices compared to arrays is not fixed, you can append elements, may increase the capacity of slices when appending.     //White is a collection in Java    //Slice use make to create: T represents the type of slice element being created.     the//function make accepts a type, a length (the initialization length when the tile is created), and an optional capacity parameter. When make is called, an array is allocated internally and the corresponding slice of the array is returned.     //var numbers []int = make ([]int, 5, 5)Numbers: = []int{0,1,2,3,4,5,6,7,8,9,Ten, One, A} FMT. PRINTLN (Numbers) fmt. Println ("numbers[1:4] = =", numbers[1: 4])/ * Default lower limit is 0*/Fmt. Println ("numbers[:3] = =", numbers[: 3])/* The default upper limit is Len (s) */Fmt. Println ("numbers[4:] = =", numbers[4:]) fmt. Println ("Calculate the tile's capacity:",Cap(numbers)) Fmt. Println ("Calculate the length of the slice:",Len(numbers)) Numbers =Append(Numbers, -) FMT. Println (after appending the element:, numbers)//Remove the element labeled 9Numbers =Append(numbers[: 9], numbers[Ten:]...) Fmt. Println ("After deleting the element at the specified location:", numbers)//Delete the last element of a sliceNumbers =Append(numbers[:Len(Numbers)-1], numbers[Len(numbers):] ...) Fmt. Println ("Delete the last element of a slice:", numbers) fmt. Println ("Calculate the length of the slice:",Len(numbers))varNumber1 []int    ifNumber1 = =Nil{FMT. Println ("Slice is empty")    }//Create map    varCountrycapitalmapMap[string]string    / * Create a collection * /Countrycapitalmap = Make(Map[string]string)/ * Map Insert Key-value pairs, each country corresponding to the capital * *countrycapitalmap["France"] ="Paris"countrycapitalmap["Italy"] ="Rome"countrycapitalmap["Japan"] ="Tokyo"countrycapitalmap["India"] ="New Delhi"Fmt. Println (countrycapitalmap["India"])/ * Use key to output map values * /     forCountry: =RangeCountrycapitalmap {fmt. Println (" Capital of", Country,"is", Countrycapitalmap[country])}/ * To see if the element exists in the collection * /Captial, OK: = countrycapitalmap["India"]/ * If OK is true, then exists, otherwise does not exist * /    ifOK {fmt. Println ("Capital of India is----", Captial)}Else{FMT. Println ("Capital of states are not present")    }//Implement two structural bodies    varPhone Phone phone =New(IPhone) phone.call () phone =New(Xiaomi) Phone.call ()}//functionfuncTestFun1 () {fmt. Println ("function")}funcTestFun2 (NUM1int, num2int) {FMT. Println ("function parameter", num1+num2)}//function returns a single valuefuncTESTFUN3 (NUM1int, num2int)int{returnNUM1 + num2}//function returns multiple valuesfuncTestFun4 (NUM1int, num2int) (int,int) {returnNUM1 + num2, num1-num2}//define interfaces use different structures to create different methods to inherit the interfacetypePhoneInterface{//methods in the interfaceCall ()}//define Structure bodytypeIphonestruct{}//define the methods in the interfacefunc(iphone iphone) call () {FMT. Println ("The phone you use is an apple.")}//define another structure bodytypeXiaomistruct{}//define the methods in the interfacefunc(Xiaomi Xiaomi) call () {FMT. Println ("You use the phone is millet:")}