JAVA

list to int array in java 8

int[] array = list.stream().mapToInt(i->i).toArray();

how to convert int array to Integer List in java

int[] ints = {1,2,3};
List<Integer> list = Arrays.stream(ints).boxed().collect(Collectors.toList());

convert int array to integer list java

int[] arr = {1,2,3};
IntStream.of(arr).boxed().collect(Collectors.toList());

int array to integer arraylist

import java.util.*;
import java.util.stream.Collectors; 

// java 8+
List<Integer> list = Arrays.stream(nums).boxed().collect(Collectors.toList());

// java 16+
List<Integer> list = Arrays.stream(nums).boxed().toList();

convert list of integer to array in java

List<Integer> al = new ArrayList<Integer>(); 
Integer[] arr = new Integer[al.size()]; 
arr = al.toArray(arr); 

convert int[] to list java

int arr[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
List lst = Arrays.asList(arr);
System.out.println(lst.size());

convert array of int to arraylist java

int[] ints = {1, 2, 3};
List<Integer> intList = new ArrayList<Integer>(ints.length);
for (int i : ints)
{
    intList.add(i);
}

List of Integer to int array

int[] example1 = list.stream().mapToInt(i->i).toArray();
// OR
int[] example2 = list.stream().mapToInt(Integer::intValue).toArray();

List of Integer to int array

int [] ints = list.stream().mapToInt(Integer::intValue).toArray();

convert list to int array

 list.stream().mapToInt(i->i).toArray();

java int array to Integer ArrayList

int[] ints = {1, 2, 3};
List<Integer> intList = new ArrayList<Integer>(ints.length);
for (int i : ints)
{
    intList.add(i);
}

Java 7. Converting List> to int[][]:

// original list
List<List<Integer>> list = Arrays.asList(
        Arrays.asList(1, 2),
        Arrays.asList(2),
        Arrays.asList(3));
// initialize the array,
// specify only the number of rows
int[][] arr = new int[list.size()][];
// iterate through the array rows
for (int i = 0; i < arr.length; i++) {
    // initialize the row of the array,
    // specify the number of elements
    arr[i] = new int[list.get(i).size()];
    // iterate through the elements of the row
    for (int j = 0; j < arr[i].length; j++) {
        // populate the array
        arr[i][j] = list.get(i).get(j);
    }
}
// output
System.out.println(Arrays.deepToString(arr));
// [[1, 2], [2], [3]]