是否可以使 HashSet 与任何对象一起工作?我试图让对象实现 可以比较,但没有帮助
import java.util.HashSet;
public class TestHashSet {
public static void main(String[] args) {
class Triple {
int a, b, c;
Triple(int aa, int bb, int cc) {
a = aa;
b = bb;
c = cc;
}
}
HashSet<Triple> H = new HashSet<Triple>();
H.add(new Triple(1, 2, 3));
System.out.println(H.contains(new Triple(1, 2, 3)));//Output is false
}
}
最佳答案
您需要实现equals(Object)
和 hashCode()
确保对象相等时哈希码也相等
在您的示例中:
class Triple {
int a, b, c;
Triple(int aa, int bb, int cc) {
a = aa;
b = bb;
c = cc;
}
public boolean equals(Object arg){
if(this==arg)return true;
if(arg==null)return false;
if(arg instanceof Triple){
Triple other = (Triple)arg;
return this.a==other.a && this.b==other.b && this.c==other.c;
}
return false;
}
public int hashCode(){
int res=5;
res = res*17 + a;
res = res*17 + b;
res = res*17 + c;
//any other combination is valid as long as it includes only constants, a, b and c
return res;
}
}
关于java - 如何使 java HashSet/HashMap 与任何对象一起工作?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/7214732/