英文:
How to check whether two sets contain the same objects
问题
我有一个类 IntegerType:
public class IntegerType implements DataType {private int value;public IntegerType(int value) {this.value = value;}@Overridepublic NativeType nativeType() {return NativeType.INTEGER;}@Overridepublic int size() {return Integer.BYTES;}@Overridepublic Integer value() {return this.value;}@Overridepublic boolean equals(Object o) {boolean result = false;if (o == null || o.getClass() != getClass()) {result = false;} else {IntegerType integerType = (IntegerType) o;if (this.value == integerType.value()) {result = true;}}return result;}}
而我实际上想要检查两个包含 IntegerType 实例的集合是否相同，基于这些实例是否具有相同的 .value 参数：
IntegerType int1 = new IntegerType(1);IntegerType int2= new IntegerType(1);Set<IntegerType> set1 = new HashSet<>();set1.add(int1);Set<IntegerType> set2 = new HashSet<>();set2.add(int2);System.out.println(set1.equals(set2));
然而，运行上述代码会输出 false。根据我理解的情况，它应该输出 true，因为 int1.equals(int2) 是 true。我在这里漏掉了什么？
英文:
I have a class IntegerType:
public class IntegerType implements DataType {private int value;public IntegerType(int value) {this.value = value;}@Overridepublic NativeType nativeType() {return NativeType.INTEGER;}@Overridepublic int size() {return Integer.BYTES;}@Overridepublic Integer value() {return this.value;}@Overridepublic boolean equals(Object o) {boolean result = false;if (o == null || o.getClass() != getClass()) {result = false;} else {IntegerType integerType = (IntegerType) o;if (this.value == integerType.value()) {result = true;}}return result;}}
And I essentially want to check whether two sets containing instances of IntegerType are the same based on whether the instances have the same .value parameter:
IntegerType int1 = new IntegerType(1);IntegerType int2= new IntegerType(1);Set<IntegerType> set1 = new HashSet<>();set1.add(int1);Set<IntegerType> set2 = new HashSet<>();set2.add(int2);System.out.println(set1.equals(set2));
However running the above code prints out false. From what I understand it should print true since int1.equals(int2) is true. What am I missing here?
答案1
得分: 2
就像名字所示，HashSet 要求你重写 hashCode 方法，它用来确定两个对象是否可能相等。以下是一种可能的实现：
@Overridepublic int hashCode() {final int prime = 31;int result = 1;result = prime * result + value;return result;}
英文:
As the name suggests, HashSet requires you to override the hashCode method, which it uses to determine whether or not two objects could possibly be equal. Here is a possible implementation:
@Overridepublic int hashCode() {final int prime = 31;int result = 1;result = prime * result + value;return result;}
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论