CODEWITHSUNDEEP
javaeclipse
FrancisGeek
FrancisGeek

Reputation: 147

No output in Eclipse

As I learn Algorithms Book authoried by Robert Sedgewick,when I complete the Selection.java code , I find that there is no output,I hardly know why.

Below is my code.

import java.util.Comparator;

import edu.princeton.cs.algs4.StdIn;
import edu.princeton.cs.algs4.StdOut;

public class Selection {
    public static void sort(Comparable[] a) {
        int n = a.length;
        for (int i = 0; i < n; i++) {
            int min = i;
            for (int j = i + 1; j < n; j++)
                if (less(a[j], a[min]))
                    min = j;
            exch(a, i, min);
        }
    }

    private static boolean less(Comparable v, Comparable w) {
        return v.compareTo(w) < 0;
    }

    private static boolean less(Comparator comparator, Object v, Object w) {
        return comparator.compare(v, w) < 0;
    }

    private static void exch(Object[] a, int i, int j) {
        Object swap = a[i];
        a[i] = a[j];
        a[j] = swap;
    }

    /***************************************************************************
     * Check if array is sorted - useful for debugging.
     ***************************************************************************/

    // is the array a[] sorted?
    private static boolean isSorted(Comparable[] a) {
        return isSorted(a, 0, a.length - 1);
    }

    // is the array sorted from a[lo] to a[hi]
    private static boolean isSorted(Comparable[] a, int lo, int hi) {
        for (int i = lo + 1; i <= hi; i++)
            if (less(a[i], a[i - 1]))
                return false;
        return true;
    }

    // is the array a[] sorted?
    private static boolean isSorted(Object[] a, Comparator comparator) {
        return isSorted(a, comparator, 0, a.length - 1);
    }

    // is the array sorted from a[lo] to a[hi]
    private static boolean isSorted(Object[] a, Comparator comparator, int lo,
            int hi) {
        for (int i = lo + 1; i <= hi; i++)
            if (less(comparator, a[i], a[i - 1]))
                return false;
        return true;
    }

    // print array to standard output
    private static void show(Comparable[] a) {
        for (int i = 0; i < a.length; i++) {
            StdOut.println(a[i]);
        }
    }

    public static void main(String[] args) {
        String[] a = StdIn.readAllStrings();
        // Selection.sort(a);
        show(a);
    }
}

And then is my two test

1.http://algs4.cs.princeton.edu/21elementary/tiny.txt

S O R T E X A M P L E

2.http://algs4.cs.princeton.edu/21elementary/words3.txt

bed bug dad yes zoo now for tip ilk dim tag jot sob nob sky hut men egg few jay owl joy rap gig wee was wad fee tap tar dug jam all bad yet

I expect the increasing order in the output,but there is no output. And I set the Run Configuration--Commman Tab --Input File as ~/tiny.txt But when I apply and run,there is no output(I use Eclipse Mars 4)

Then I guess maybe the parameter or type Comparable,Because there is a lot warning of it,but I can't handle it. Anyone could tell me how to solve the problem:)

Upvotes: 1

Views: 167

Answers (1)

James Jithin
James Jithin

Reputation: 10555

edu.princeton.cs.algs4.StdOut internally uses PrintWriter initialized as out = new PrintWriter(new OutputStreamWriter(System.out, CHARSET_NAME), true);. The println methods just write to the stream, but does not flush. You may either do:

  • StdOut.print() at the end of your writing which intern calls out.flush()
  • StdOut.print(Object o) method which always calls flush()

Reference: StdOut.java

Upvotes: 1

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