GeneratorExamples.java

package ch.akuhn.util;


public class GeneratorExamples {

    public static void main(String[] args) {

        Generator<Integer> fibonacci = new Generator<Integer>() {
            @Override
            public void run() {
                int a = 0, b = 1;
                while (true) {
                    a = b + (b = a);
                    yield(a);
                }
            }
        };

        for (int x : fibonacci) {
            if (x > 20000) break;
            System.out.println(x);
        }
        System.out.println("done\n");

        Generator<Character> hello = new Generator<Character>() {
            @Override
            public void run() {
                String str = "Hello, Worlds!";
                for (int n = 0; n < str.length(); n++) {
                    yield(str.charAt(n));
                }
            }
        };

        for (char each : hello) {
            System.out.println(each);
        }
        System.out.println("done\n");

        Character[] array = { 'a', 'b', 'c', 'd', 'e', 'f' };
        int tally = 0;
        for (Character[] each : permute(array)) {
            Out.puts(each);
            tally++;
        }
        Out.puts(tally);

    }

    public static <T> Generator<T[]> permute(final T[] a) {
        return new Generator<T[]>() {
            private void permute(int n) {
                if (n == 0) yield(a.clone());
                else for (int k = n; k >= 0; k--) {
                    swap(n, k);
                    permute(n - 1);
                    swap(n, k);
                }
            }

            @Override
            public void run() {
                permute(a.length - 1);
            }

            private void swap(int n, int m) {
                T temp = a[n];
                a[n] = a[m];
                a[m] = temp;
            }
        };
    }

}