问题描述
//TPoint.java/* This is just a trivial "struct" type class -- it simply holds an int x/y point for use by Tetris, and supports equals() and toString(). We'll allow public access to x/y, so this is not an object really. */public class TPoint {public int x;public int y;// Creates a TPoint based in int x,ypublic TPoint(int x, int y) {// questionable style but convenient --// params with same name as ivarsthis.x = x;this.y = y;}// Creates a TPoint, copied from an existing TPointpublic TPoint(TPoint point) {this.x = point.x;this.y = point.y;}// Standard equals() overridepublic boolean equals(Object other) {// standard two checks for equals()if (this == other) return true;if (!(other instanceof TPoint)) return false;// check if other point same as usTPoint pt = (TPoint)other;return(x==pt.x && y==pt.y);}// Standard toString() override, produce// human-readable String from objectpublic String toString() {return "(" + x + "," + y + ")";}}import java.util.HashSet;public class test {/** * @param args */public static void main(String[] args) {TPoint a =new TPoint(0,1);TPoint b =new TPoint(0,1);HashSet<TPoint> setA = new HashSet<TPoint>();HashSet<TPoint> setB = new HashSet<TPoint>();setA.add(a);setB.add(b);boolean res = setA.equals(setB);System.out.println(res);}} 问题补充：redstarofsleep 写道
解决方案
因为你没有重写hashCode。既然是HashSet，那么你不重写这个，Hash值都不一样，当然对不上。
解决方案二：
请重写TPoint的hashCode方法。上面的不要误人子弟。默认从Object继承来的hashCode是基于对象的ID实现的。如果你重载了equals，比如说是基于对象的内容实现的，而保留hashCode的实现不变，那么很可能某两个对象明明是“相等”，而hashCode却不一样。这样，当你用其中的一个作为键保存到hashMap、hasoTable或hashSet中，再以“相等的”找另一个作为键值去查找他们的时候，则根本找不到。
解决方案三：
你只重写了TPoint的equals方法,但是你调用的是Hashset的equals方法,Hashset的equals方法你并没有重写哦