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  • Go Arrays

Go Arrays

Arrays are used to store multiple values of the same type in a single variable, instead of declaring separate variables for each value.

Declare an Array

In Go, there are two ways to declare an array:

1. With the var keyword:

Syntax

var array_name = [length]datatype{values} // here length is defined

or

var array_name = [...]datatype{values} // here length is inferred

2. With the := sign:

Syntax

array_name := [length]datatype{values} // here length is defined

or

array_name := [...]datatype{values} // here length is inferred

Note: The length specifies the number of elements to store in the array. In Go, arrays have a fixed length. The length of the array is either defined by a number or is inferred (means that the compiler decides the length of the array, based on the number of values).

Array Examples

Example

This example declares two arrays (arr1 and arr2) with defined lengths:

package main
import ("fmt")

func main() {
  var arr1 = [3]int{1,2,3}
  arr2 := [5]int{4,5,6,7,8}

  fmt.Println(arr1)
  fmt.Println(arr2)
}

Result:

[1 2 3]
[4 5 6 7 8]

Example

This example declares two arrays (arr1 and arr2) with inferred lengths:

package main
import ("fmt")

func main() {
  var arr1 = [...]int{1,2,3}
  arr2 := [...]int{4,5,6,7,8}

  fmt.Println(arr1)
  fmt.Println(arr2)
}

Result:

[1 2 3]
[4 5 6 7 8]

Example

This example declares an array of strings:

package main
import ("fmt")

func main() {
  var cars = [4]string{"Volvo", "BMW", "Ford", "Mazda"}
  fmt.Print(cars)
}

Result:

[Volvo BMW Ford Mazda]

Access Elements of an Array

You can access a specific array element by referring to the index number.

In Go, array indexes start at 0. That means that [0] is the first element, [1] is the second element, etc.

Example

This example shows how to access the first and third elements in the prices array:

package main
import ("fmt")

func main() {
  prices := [3]int{10,20,30}

  fmt.Println(prices[0])
  fmt.Println(prices[2])
}

Result:

10
30

Change Elements of an Array

You can also change the value of a specific array element by referring to the index number.

Example

This example shows how to change the value of the third element in the prices array: 

package main
import ("fmt")

func main() {
  prices := [3]int{10,20,30}

  prices[2] = 50
  fmt.Println(prices)
}

Result:

[10 20 50]

Array Initialization

If an array or one of its elements has not been initialized in the code, it is assigned the default value of its type.

Tip: The default value for int is 0, and the default value for string is "".

Example

package main
import ("fmt")

func main() {
  arr1 := [5]int{} //not initialized
  arr2 := [5]int{1,2} //partially initialized
  arr3 := [5]int{1,2,3,4,5} //fully initialized

  fmt.Println(arr1)
  fmt.Println(arr2)
  fmt.Println(arr3)
}

Result:

[0 0 0 0 0]
[1 2 0 0 0]
[1 2 3 4 5]

Initialize Only Specific Elements

It is possible to initialize only specific elements in an array.

Example

This example initializes only the second and third elements of the array: 

package main
import ("fmt")

func main() {
  arr1 := [5]int{1:10,2:40}

  fmt.Println(arr1)
}

Result:

[0 10 40 0 0]

Example Explained

 The array above has 5 elements.

  • 1:10 means: assign 10 to array index 1 (second element).
  • 2:40 means: assign 40 to array index 2 (third element).

Find the Length of an Array

The len() function is used to find the length of an array:

Example

package main
import ("fmt")

func main() {
  arr1 := [4]string{"Volvo", "BMW", "Ford", "Mazda"}
  arr2 := [...]int{1,2,3,4,5,6}

  fmt.Println(len(arr1))
  fmt.Println(len(arr2))
}

Result:

4
6
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