任何 Int 上的 Scala 方法 hashCode() 是相同的数字吗？

Question

为什么任何 Int 上的 Scala 方法 hashCode() 返回相同的数字

Answer 1

因为整数的 hashCode 就是这样定义的。

它满足the contract很好:

• If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.

最重要的是，它符合建议

• It is not required that if two objects are unequal according to the equals(java.lang.Object) method, then calling the hashCode method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hashtables

事实上，这是一个 perfect hash function 的例子.