Repeat.java

Below is the syntax highlighted version of Repeat.java from §4.1 Performance.

/******************************************************************************
 *  Compilation:  javac Repeat.java
 *  Execution:    java Repeat n
 *  Dependencies: Stopwatch.java
 *
 *  Create a string that contains n copies of the letter 'x'.
 *
 ******************************************************************************/

public class Repeat {

    public static String method1(int n) {
        if      (n == 0) return "";
        String temp = method1(n/2);
        if (n % 2 == 0) return temp + temp;
        else            return temp + temp + "x";
    }

    public static String method2(int n) {
        String s = "";
        for (int i = 0; i < n; i++)
            s = s + "x";
        return s;
    }

    public static String method3(int n) {
        if      (n == 0) return "";
        else if (n == 1) return "x";
        else return method3(n/2) + method3(n - n/2);
    }


    public static String method4(int n) {
        char[] temp = new char[n];
        for (int i = 0; i < n; i++)
            temp[i] = 'x';
        return new String(temp);
    }


    public static void main(String[] args) {
        int n = Integer.parseInt(args[0]);

        Stopwatch timer = new Stopwatch();
        String s = method4(n);
        // StdOut.println(method4(n));
        StdOut.println("Elapsed time for method 4 = " + timer.elapsedTime());

        timer = new Stopwatch();
        s = method3(n);
        // StdOut.println(method3(n));
        StdOut.println("Elapsed time for method 3 = " + timer.elapsedTime());

        timer = new Stopwatch();
        s = method1(n);
        // StdOut.println(method1(n));
        StdOut.println("Elapsed time for method 1 = " + timer.elapsedTime());

        timer = new Stopwatch();
        s = method2(n);
        // StdOut.println(method2(n));
        StdOut.println("Elapsed time for method 2 = " + timer.elapsedTime());
    }

}