Go Language for Java Developers Part 4

Variable: A variable is a storage location for holding a value. The set of permissible values is determined by the variable’s type.
 Java language has primitive type and objects, both have different syntax to declare a variable either Primitive type or Object type.

Animal a = new Animal() 
Student s = new Student()

Java is object oriented language so that we can have access modifier for variable declaration

private int a 
public String b 
protected float c 
private Animal a

In the Java we can declare a variable at many places like Local variable, Parameters, Class level, Instance variable.\

Variable Naming

1. Variable names are case-sensitive
2. An unlimited-length sequence of Unicode letters and digits
3. Beginning with a letter, the dollar sign “$”, or the underscore character “_”.
4. No special characters allowed as identifier of variable
5. We can’t use reserved keywords

Variables in Go are created by first using the ‘var’ keyword, then specifying the variable name, the type and finally assigning a value to the variable.

package main
import "fmt"
func main() {
 var x int // Line 1 
 x = 10 // Line 2 
 var y string = "Hello Go!" // Line 3 
 fmt.Println(x) 
 fmt.Println(y) 
}

In Line 1, var indicates it’s variable, x is a name of variable and int is a type of variable. In Line 2, we are assigning value in x variable. In Line 3, we have declares string variable and assign in single line
 Since creating a new variable with a starting value is so common Go also supports a shorter statement:

y:= "Hello Go!"

With above a shorter a syntax Go compiler will automatically identify that y is variable of type string and value is “Hello Go!”.
 Declare multiple variables at same time

var ( name string 
      age int
      location string 
    )

Go is not object oriented language so we don’t have access modifier like we have in Java. In Go language, We have two place to declare variables

1. Inside Function 2. Out Side Function.\

Function / Local Variable

package main
import "fmt"
func main(){
    var x int = 10  
    fmt.Println(x)
}

Global Variable: Any function can access y variable, x is local variable only accessible inside main function

package main
import "fmt"
var y int =10
func main(){
    var x int = 10
    fmt.Println(x)
    fmt.Println(y)
}
func hello(){
    fmt.Println(y)
}

Variable Name

1. [Name must be start with letter]{#815b}
2. [Name may contain letter, number and underscore (_)]{#ea86}
3. [Name is character sensetive Num and num consider as two different variable]{#b8cb}