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Go For Java Developers


Data Types:

  1. String  --> string (defaults to "")
  2. Integer --> int    (defaults to 0)
  3. Double --> float (defaults to 0.0)
  4. Boolean --> bool (defaults to false)
    final equivalent
     const x string = "text" 

    Define 

    String x   -->    var x string
  

   Initialize

    x = "text" --> x = "text"
  
  Define & Initialize
    String x = "text" --> x := "text"

   Collection

     List list = new ArrayList<>();   --> var list []string
                                                                      --> list := []string{"text"}
                                                                      --> list = append(list, "another text")

    Map map = new HashMap<>():

       var x map[string]int  where string is key and int is value.
       x["key1"] = 10
      
   Control Statements
     if/for/switch
     
    if (condition) {} --> if (condition) {}
    e.g.
     if (10 >= 10) {} --> if (10 >= 10) {}

    for(initialization;condition;incr/decr) {} --> for (initialization;condition;incr/decr) {}
    for (int x = 0; x < 10; x++) {} --> for (x := 0; x < 10; x++) {}

    switch(condition) {
      case A: 
         //
         break;
      case B:
        //
        break;
      default:
    }

   Go equivalent
    switch condition {
      case A: 
         //
      case B:
        //
      default:
    }
   
   Functions
     public static Integer add(int x, int y) {
        return x + y;
     }

     Go equivalent
     func Add(x int, y int) int {   // capital function name means public/package-visible
        return x + y;
     }
     
      Functions can also return multiple values
      func AddSub(x, y int) (int, int) {
        return x+y, x-y
      }
      
      Go supports closures as well.
      Kind of an anonymous function and can be assigned to a variable, e.g.
      func main() {
        add := function (x, y int) int { return x+y }
        add(1,1)
      }

     Structs & Methods
      Go doesn't support classes, nor inheritance. Use structs and methods to encapsulate data and operations e.g.

      type user struct { name string, age int } 
      structs can also contain embedded types e.g.
      type account struct {employee user, id int }

     Initialize Struct
          x := new(user)
          x := &user{}
          x := &user{}

      Composition
         type Account struct { 
            *User // this structs will act like primary member.
             id int
        }
      
     Go supports method that which are visible on on struct types e.g.
     func (a account) printName() {  
         // prints name
     }
         // not (u user) means this method is part of the struct
        // and can be called on the struct type e.g.
       func main() {
         p := account{
                   employe = {name := "xyz", age = 20},
                   id = 100000
       }
       p.printName() // note sends copy of p not a reference to p. To send a reference you'll to change printName function's signature to func (a *account) printName() {}

   
      packages
       Go packages are always a single value. e.g.
          package db
          package app
       But imports needs to full path e.g.
         package app/db


     Interfaces

       type Logger interface { 
          Log(message string)
       }
       
      Implementing an interface in Go requires just creating method with same signature e.g.
      type ConsoleLogger struct {}
      func (l *ConsoleLogger) Log(message string) {}


     Go doesn't have any exception handling, but built-in type can be used.
      type error interface { Error() string } // built-in error interface

      import ( "errors" ) 
      func process(count int) error {
           if count < 1 { 
              return errors.New("Invalid count") 
      }

     Finally equivalent in go is defer e.g.
      defer file.close()






     
                                                             
   

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