How to create multidimension arrays

[Java Tip]

import java.util.Random;

public class MultiDimArray {

  static Random rand = new Random();

  public static void main(String[] args) {
    int[][] a1 = { { 1, 2, 3, }, { 4, 5, 6, }, };
    for (int i = 0; i < a1.length; i++)
      for (int j = 0; j < a1[i].length; j++)
        System.out.println("a1[" + i + "][" + j + "] = " + a1[i][j]);
    // 3-D array with fixed length:
    int[][][] a2 = new int[2][2][4];
    for (int i = 0; i < a2.length; i++)
      for (int j = 0; j < a2[i].length; j++)
        for (int k = 0; k < a2[i][j].length; k++)
          System.out.println("a2[" + i + "][" + j + "][" + k + "] = "
              + a2[i][j][k]);
    // 3-D array with varied-length vectors:
    int[][][] a3 = new int[rand.nextInt(7)][][];
    for (int i = 0; i < a3.length; i++) {
      a3[i] = new int[rand.nextInt(5)][];
      for (int j = 0; j < a3[i].length; j++)
        a3[i][j] = new int[rand.nextInt(5)];
    }
    for (int i = 0; i < a3.length; i++)
      for (int j = 0; j < a3[i].length; j++)
        for (int k = 0; k < a3[i][j].length; k++)
          System.out.println("a3[" + i + "][" + j + "][" + k + "] = "
              + a3[i][j][k]);
    // Array of nonprimitive objects:
    Integer[][] a4 = { { new Integer(1), new Integer(2) },
        { new Integer(3), new Integer(4) },
        { new Integer(5), new Integer(6) }, };
    for (int i = 0; i < a4.length; i++)
      for (int j = 0; j < a4[i].length; j++)
        System.out.println("a4[" + i + "][" + j + "] = " + a4[i][j]);
    Integer[][] a5;
    a5 = new Integer[3][];
    for (int i = 0; i < a5.length; i++) {
      a5[i] = new Integer[3];
      for (int j = 0; j < a5[i].length; j++)
        a5[i][j] = new Integer(i * j);
    }
    for (int i = 0; i < a5.length; i++)
      for (int j = 0; j < a5[i].length; j++)
        System.out.println("a5[" + i + "][" + j + "] = " + a5[i][j]);
    // Output test
    int ln = 0;
    for (int i = 0; i < a3.length; i++)
      for (int j = 0; j < a3[i].length; j++)
        for (int k = 0; k < a3[i][j].length; k++)
          ln++;

  }
}