[Q#2707357][A#2707431] how to create dynamic two dimensional array in java?

https://stackoverflow.com/q/2707357

I want to create a two dimensional array dynamically. I know the number of columns. But the number of rows are being changed dynamically. I tried the array list, but it stores the value in single dimension only. What can I do?

Answer

https://stackoverflow.com/a/2707431

Since the number of columns is a constant, you can just have an List of int[]. Since it's backed by a List, the number of rows can grow and shrink dynamically. Each row is backed by an int[], which is static, but you said that the number of columns is fixed, so this is not a problem.

APIzation

import java.util.*;
    //...

    List<int[]> rowList = new ArrayList<int[]>();

    rowList.add(new int[] { 1, 2, 3 });
    rowList.add(new int[] { 4, 5, 6 });
    rowList.add(new int[] { 7, 8 });

    for (int[] row : rowList) {
        System.out.println("Row = " + Arrays.toString(row));
    } // prints:
      // Row = [1, 2, 3]
      // Row = [4, 5, 6]
      // Row = [7, 8]

    System.out.println(rowList.get(1)[1]); // prints "5"

package com.stackoverflow.api;

import java.util.ArrayList;
import java.util.List;

public class Human2707431 {

  public static List<int[]> create2DArray(
    int[] array,
    int[] array1,
    int[] array2
  ) {
    List<int[]> rowList = new ArrayList<>();

    rowList.add(array);
    rowList.add(array1);
    rowList.add(array2);

    return rowList;
  }
}

package com.stackoverflow.api;

import java.util.*;

/**
 * how to create dynamic two dimensional array in java?
 *
 * @author APIzator
 * @see <a href="https://stackoverflow.com/a/2707431">https://stackoverflow.com/a/2707431</a>
 */
public class APIzator2707431 {

  public static void createArray(List<int[]> rowList) throws Exception {
    // ...
    for (int[] row : rowList) {
      System.out.println("Row = " + Arrays.toString(row));
    }
    // prints:
    // Row = [1, 2, 3]
    // Row = [4, 5, 6]
    // Row = [7, 8]
    // prints "5"
    System.out.println(rowList.get(1)[1]);
  }
}