Simple understanding of why to rewrite hashcode and equals methods at the same time

Knowledge point ：

1. If two objects use equals Unequal , be hashcode Must be different

Why?

Because love .

We know set Collections do not allow duplicate elements , How can we ensure that there is no repetition . use equals The method is enough . But once there's a lot of data , When that object is compared with the objects in the collection , Call... Every time equals Method , and equals The method is realized by == Realized , Compare addresses , The address can only be obtained by accessing the bottom layer , So the line efficiency is low .
How to solve it ？ Is to rewrite hashcode Method , and hashcode It's self generated , No access to the underlying , This can be viewed String Source code ,

Every time I compare , Compare first hashCode, If it's not equal , Then there's no need to compare , Go straight back to false, If equal , I call again equals Methods for comparison , This improves efficiency .