gbajaj

import java.util.ArrayList;
import java.util.Arrays;

// Your ArrayList of Integers
ArrayList<Integer> arrayList = new ArrayList<>(Arrays.asList(1, 2, 3, 4, 5));

// Convert it to a primitive int[] array
int[] primitiveArray = arrayList.stream()
                                .mapToInt(Integer::intValue)
                                .toArray();

gbajaj

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

public class CustomRecordExample {

  // Your static nested class is defined here
  static class Record {
    int first;

gbajaj

fun main() {
    // 1. Define an empty mutable 2D list
    val twoDList = mutableListOf<MutableList<Int>>()
    println("1. Initial empty mutable list: $twoDList")

    // 2. Add inner lists to it later
    twoDList.add(mutableListOf(10, 20, 30))
    twoDList.add(mutableListOf(40, 50, 60))
    println("2. Mutable list after adding rows: $twoDList")

gbajaj

/**
 * Example:
 * var ti = TreeNode(5)
 * var v = ti.`val`
 * Definition for a binary tree node.
 * class TreeNode(var `val`: Int) {
 *     var left: TreeNode? = null
 *     var right: TreeNode? = null
 * }
 */