Java Bucket Sort Algorithm Example

This Java source code example demonstrates the usage of the Bucket sort algorithm in Java programming language.

Java Bucket (non-comparison) Sort Algorithm Example

Sorting positive integers with Bucket (non-comparison) sort algorithm:

import java.util.Arrays;

public class BucketSortExample {

    private static int[] doBucketSort(int[] vals, int max) {

        // creates empty bucket and sorted array objects
        int[] bucket = new int[max + 1];
        int[] sorted_vals = new int[vals.length];

        // each value is an index in the bucket having value 1
        // if there are same values, the index is incremented
        for (int i = 0; i < vals.length; i++) {
            bucket[vals[i]]++;
        }

        int outPos = 0;

        // the bucket elements with non zero values are added
        // to the sorted_values array
        for (int i = 0; i < bucket.length; i++) {
            for (int j = 0; j < bucket[i]; j++) {
                sorted_vals[outPos++] = i;
            }
        }

        return sorted_vals;
    }

    // calculates max value
    private static int max(int[] vals) {

        int max = 0;

        for (int i = 0; i < vals.length; i++) {
            if (vals[i] > max) {
                max = vals[i];
            }
        }

        return max;
    }

    public static void main(String args[]) {

        int[] rnums = {
            3,
            2,
            2,
            1,
            16,
            7,
            12,
            1,
            7,
            0,
            23
        };

        int maxValue = max(rnums);

        System.out.println("Original array: ");
        System.out.println(Arrays.toString(rnums));

        System.out.println("Sorted array: ");

        int[] sorted = doBucketSort(rnums, maxValue);
        System.out.println(Arrays.toString(sorted));
    }
}

Output

Original array: 
[3, 2, 2, 1, 16, 7, 12, 1, 7, 0, 23]
Sorted array: 
[0, 1, 1, 2, 2, 3, 7, 7, 12, 16, 23]