JAVA

integer arraylist to int array

//only works in java 8 or later
list.stream().mapToInt(i -> i).toArray();

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 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);
}

arraylist to int array conversion in java

//use this if you don't want to use any methods to convert an
//arrayList(with the same size as required array) to a 'int[]' type.
//Also, this is only useful when you know the size of the array you're working with.

  int[] array = new int[size];
  for (int i = 0; i < array.length; i++) {
      ans[i] = arraylist.get(i);
  }
// array will be now of int[] type

// Also as @FineFinch pointed it could be done using :
    //only works in java 8 or later
    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);
}

convert arraylist to array int

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

convert Integer arraylist to array java

Your_ArrayList_Name.stream().mapToInt(k->k).toArray();