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.mkyong.array;
import java.util.ArrayList;
import java.util.List;
public class ArrayExample1 {
public static void main(String[] args) {
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.mkyong.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 ArrayExample2 {
public static void main(String[] args) {
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]
References
- IntStream JavaDoc
- Java – Convert Array to Stream