import java.util.TreeSet;import org.junit.Test;public class TestTreeSet {	class Combine implements Comparable<Combine> {		private int p1;		private int p2;		public Combine(int p1, int p2) {			this.p1 = p1;			this.p2 = p2;		}		@Override		    public int hashCode() {			return p1 * 31 + p2;		}		@Override		    public Boolean equals(Object obj) {			System.out.print("whether equal " + this + " and " + obj);			Boolean rect = false;			if (obj instanceof Combine) {				System.out.println("whether equal " + this + " and " + obj);				Combine other = (Combine) obj;				rect = (this.p1 == other.getP1() && this.p2 == other.getP2());			}			System.out.println(": " + rect);			return rect;		}		@Override		    public int compareTo(Combine o) {			System.out.print("compare " + this + " and " + o);			// 排序時只考慮p1			if (this.p1 < o.p1) {				System.out.println(", return -1");				return -1;			} else if (this.p1 > o.p1) {				System.out.println(", return 1");				return 1;			} else {				System.out.println(", return 0");				return 0;			}		}		@Override		    public String toString() {			return "(" + p1 + "," + p2 + ")";		}		public int getP1() {			return p1;		}		public void setP1(int p1) {			this.p1 = p1;		}		public int getP2() {			return p2;		}		public void setP2(int p2) {			this.p2 = p2;		}	}	@Test	  public void test() {		Combine c1 = new Combine(1, 2);		Combine c2 = new Combine(1, 2);		Combine c3 = new Combine(1, 3);		Combine c4 = new Combine(5, 2);		TreeSet<Combine> set = new TreeSet<Combine>();		set.add(c1);		set.add(c2);		set.add(c3);		set.add(c4);		while (!set.isEmpty()) {			//按順序輸出TreeSet中的元素			Combine combine = set.pollFirst();			System.out.println(combine.getP1() + "/t" + combine.getP2());		}	}}