之所以hashCode相等,却可以equal不等,就比如ObjectA和ObjectB他们都有属性name,那么hashCode都以name计算,所以hashCode一样,但是两个对象属于不同类型,所以equal为false。 4、 为什么需要hashCode? 1、 通过hashCode可以很快的查到小内存块。 2、通过hashCode比较比equal方法快,当get时先比较hashCode,如果hashCode不同,直...
hashcode本身的动作是在堆上的对象产生了一个独特的值,而如果没有重写hashcode,那么两个class对象无论如何都不会相等,就算这两个class对象指向了相同的数据 我们来做个测试,只重写equals public static void main(String[] args) throws Exception { Info info = new Info("test"); Info info1 = new Info("t...
hashCode()方法和equals()方法的作用其实一样,在Java里都是用来对比两个对象是否相等一致。 Equal 没有重写的equal 使用是继承自 Object 的 equal 方法,和“==” 的作用一样, 比较两个对象的内存地址是否相等。 public boolean equals(Object obj) { return (this == obj); } 重写过的 equal, 比较的是两...
程序猿的日常——Java基础之equals与hashCode equals和hashCode是我们日常开发最常使用的方法,但是因为一般都使用默认的规则,因此也很少会引起关注。不过了解他们的用途和设计的原则,还是会帮助我们更好的设计代码。 equals equals是java很基础的一个问题,通常都会跟==来做比较。那么看看下...
但是java的普通对象，里面的值，可能是会变的，真正用来比较对象的时候 java其实对比的是两个对象的id ...
@TestpublicvoidprimitivesShouldBeEqual(){inti =4;intj =4; assertTrue(i == j); } Example 1 In Example 1, we can see thatCarTestwill pass forprimitivesShouldBeEqual, since the equality operator==inherently works for primitives. The two primitive values i and j are assigned respectively as ...
Objects that are equal (according to theirequals()) must return the same hash code.Different objects do not need to return different hash codes. The general contract ofhashCode()states: Whenever it is invoked on the same object more than once during an execution of a Java application,hashCode...
equals(Object otherObject)– verifies the equality of two objects. It’s default implementation simply checks the object references of two objects to verify their equality. By default, two objects are equal if and only if they refer to the same memory location. Most Java classes override this ...
Java SE defines the contract that our implementation of theequals()method must fulfill. In short, most criteria follow common sense but we can define the formal rules that theequals()method must follow. It must be: reflexive: an object must equal itself ...
multiple new instances in set: Will the following work or not: HashSet someSet = new HashSet(); someSet.add(new PersistentClass()); someSet.add(new PersistentClass()); assert(someSet.size() == 2); equal to same object from another session: ...