package basics.mutablebasic;
import basics.immutabledata.Pair;
public class Main {
	private Main() {}
	static public void main (final String[] args) {
		//stdlib.Trace.graphvizShowSteps (true); stdlib.Trace.run ();
		final PairBuilder<Integer,String> pb1 = new PairBuilder<Integer,String>();
		pb1.setFirst(42);
		pb1.setSecond("dog");
		System.out.println(pb1);
		final Pair<Integer,String> p1 = pb1.toPair();
		System.out.println(p1);

		final PairBuilder<Integer,String> pb2 = new PairBuilder<Integer,String>();
		final Pair<Integer,String> p2 = pb2.toPair();
	}
}
final class PairBuilder<S extends Comparable<S>, T extends Comparable<T>> {
	private S x;
	private T y;
	public PairBuilder() { }
	public void setFirst(S x) { this.x = x; }
	public void setSecond(T y) { this.y = y; }
	public Pair<S,T> toPair() {
		if (x == null || y == null)
			throw new NullPointerException();
		return new Pair<S,T>(x,y);
	}
}