HashSet衡量两个元素相等的标准代码

import java.util.HashSet;
import java.util.Scanner;
public class Main{																																																								
	
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		
		HashSet set = new HashSet();
		
		set.add(new A());
		set.add(new A());
		set.add(new B());
		set.add(new B());
		set.add(new C());
		set.add(new C());
		
		System.out.println(set);
		
		in.close();
	}
}
class A{

	

	@Override
	public boolean equals(Object obj) {
		// TODO Auto-generated method stub
		return true;
	}
	
}
class B{
	@Override
	public int hashCode() {
		// TODO Auto-generated method stub
		return 1;
	}	
}
class C{
	@Override
	public int hashCode() {
		// TODO Auto-generated method stub
		return 2;
	}

	@Override
	public boolean equals(Object obj) {
		// TODO Auto-generated method stub
		return true;
	}

}

输出结果：

因为C类 重写了equals方法和hashCode， 导致HashSet 将两个对象判成了相同元素

[B@1, B@1, C@2, A@7d4991ad, A@4aa298b7]