Creating and storing arrays in a map

Sometimes you want to create variable names dynamically, for example in a loop. One way of doing this is to not create the variables with different names but rather to store them in a Collection object that takes a key-value pair.
You can provide a unique key for the variable and then store its reference as the value.
In this examples first method we create 9 arrays which we store in a Map, each with different names. In the example below we use a TreeMap.
In the second method we print out the names of each key, and loop through the values of its value object (which is an array).

import java.util.Iterator;
import java.util.Map;
import java.util.TreeMap;

/**
*
* @author javadb.com
*/
public class Main {

    Map<String, int[]> map = new TreeMap<String, int[]>();

    /**
     * Example method for creating and storing arrays in a map
     */
    public void createArrays() {

        for (int i = 1; i <= 9; i++) {

            int[] array = new int[3];

            array[0] = i;
            array[1] = i + 1;
            array[2] = i + 2;


            map.put(("array_" + i), array);
        }
    }

    /**
     * Example method for printing arrays stored in a map
     */
    public void printArrays() {

        Iterator<String> iter = map.keySet().iterator();

        while (iter.hasNext()) {

            String arrayName = iter.next();

            int[] array = map.get(arrayName);

            System.out.println("Values for array " + arrayName + ":");
            for (int i = 0; i < array.length; i++) {
                System.out.println(array[i]);
            }
            System.out.println();
        }

    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        Main main = new Main();
        main.createArrays();
        main.printArrays();
    }
}

The output of the code above will be:

Values for array array_1:
1
2
3

Values for array array_2:
2
3
4

Values for array array_3:
3
4
5

Values for array array_4:
4
5
6

Values for array array_5:
5
6
7

Values for array array_6:
6
7
8

Values for array array_7:
7
8
9

Values for array array_8:
8
9
10

Values for array array_9:
9
10
11

Do you know your Java?
Take a Ten-Question-Java-Quiz!

Bookmark:

Search for code examples on this site