Java – How to convert a primitive Array to List

Code snippets to convert a primitive array int[] to a List<Integer> :

	int[] number = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

	List<Integer> list = new ArrayList<>();
	for (int i : number) {
    	    list.add(i);
	}

In Java 8, you can use the Stream APIs to do the boxing and conversion like this :

	List<Integer> list = Arrays.stream(number).boxed().collect(Collectors.toList());

1. Classic Example

Full example to convert a primitive Array to a List.

ArrayExample1.java

package com.favtuts.array;

import java.util.ArrayList;
import java.util.List;

public class ArrayToList {
    public static void main(String[] args) {
        convertPrimitiveArrayToListClassic();
    }

    static void convertPrimitiveArrayToListClassic() {
        int[] number = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

        List<Integer> list = convertIntArrayToList(number);
        System.out.println("list : " + list);
    }

    private static List<Integer> convertIntArrayToList(int[] input) {

        List<Integer> list = new ArrayList<>();
        for (int i : input) {
            list.add(i);
        }
        return list;

    }
}

Output

list : [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

Note: You can’t use the popular Arrays.asList to convert it directly, because boxing issue.

	int[] number = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
	// No, the return type is not what we want
	List<int[]> ints = Arrays.asList(number);

2. Java 8 Stream

Full Java 8 stream example to convert a primitive Array to a List.

ArrayExample2.java

package com.favtuts.array;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

public class ArrayToList {
    public static void main(String[] args) {
        convertPrimitiveArrayToListJava8Stream();
    }

    static void convertPrimitiveArrayToListJava8Stream() {
        int[] number = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

        // IntStream.of or Arrays.stream, same output
        //List<Integer> list = IntStream.of(number).boxed().collect(Collectors.toList());
		
        List<Integer> list = Arrays.stream(number).boxed().collect(Collectors.toList());
        System.out.println("list : " + list);
    }
}

Output

list : [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

Download Source Code

$ git clone https://github.com/favtuts/java-core-tutorials-examples

$ cd java-basic/array

References

1. IntStream JavaDoc
2. Java – Convert Array to Stream