Go Language for Java Developers Part 5

A variable is a storage location that holds a value. The set of permissible values is determined by the variable's type.

Java language has primitive types and objects, and both have different syntax to declare a variable.

Primitive type variable:

int a
String b
float c

Object type variable:

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 Java we can declare variables in many places like Local variable, Parameters, Class level, Instance variable.

Variable Naming

Variable names are case-sensitive
An unlimited-length sequence of Unicode letters and digits
Beginning with a letter, the dollar sign "$", or the underscore character "_".
No special characters allowd as identifier of variable
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 indicate it's a variable, x is the name of variable and int is the type of variable.

In Line 2, we are assigning the value in x variable.

In Line 3, we have declared a string variable and assigned 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 the above shorter syntax Go compiler will automatically identify that y is a variable of type string and its value is "Hello Go!".

Declare multiple variable 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 places to declare variables:

Inside Function
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 the y variable, while x is local variable only accessible inside the 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 Names

Name must be start with letter
Name may contain letter, number and underscore (_)
Name is character sensetive Num and num consider as two different variable

Go Language for Java Developers Part 5

Part 5 of a 5 part series that explains the Go language to Java developers.

Variable Naming

Function / Local Variable
`package main import "fmt" func main(){ var x int = 10 fmt.Println(x) }`

Global Variable

`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 Names

More Reading

Java Partner Resources

Go Language for Java Developers Part 5

Part 5 of a 5 part series that explains the Go language to Java developers.

Variable Naming

Function / Local Variable package main import "fmt" func main(){ var x int = 10 fmt.Println(x) }Global Variable

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 Names

More Reading

Java Partner Resources

Function / Local Variable
`package main import "fmt" func main(){ var x int = 10 fmt.Println(x) }`

Global Variable

`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 Names