IntegerSort.java

Below is the syntax highlighted version of IntegerSort.java from §4.2 Sorting and Searching.

/******************************************************************************
 *  Compilation:  javac IntegerSort.java
 *  Execution:    java IntegerSort < input.txt
 *
 *  Reads in sequence of integers between 0 and 99 and print them in
 *  sorted order.
 *
 *  % more input.txt
 *  98 2 3 1 0 0 0 3 98 98 2 2 2 0 0 0 2
 *
 *  % java IntegerSort < input.txt
 *  0 0 0 0 0 0 1 2 2 2 2 2 3 3 98 98 98
 *
 ******************************************************************************/

public class IntegerSort {

    public static void main(String[] args) {

        int MAX = 100;               // integers are between 0 and MAX-1
        int[] freq = new int[MAX];   // freq[i] = number of occurrences of i

        // read in values and calculate frequencies
        while (!StdIn.isEmpty()) {
            int i = StdIn.readInt();
            if (i < 0 || i >= MAX) throw new RuntimeException("Invalid integer");
            freq[i]++;
        }


        // print values in sorted order
        for (int i = 0; i < MAX; i++) {
            for (int j = 0; j < freq[i]; j++) {
                StdOut.print(i + " ");
            }
        }
        StdOut.println();
    }

}