The equals contract First of all, there are five conditions that our equals implementation have to comply with. These are all actually pretty straightforward, so let’s go through some examples and see what they
下面是hashCode()方法的源码 /*** Returns a hash code value for the object. This method is* supported for the benefit of hash tables such as those provided by* {@link java.util.HashMap}.* * The general contract of {@code hashCode} is:* * Whenever it is invoked on the same object m...
* ({@code x == y} has the value {@code true}). * * Note that it is generally necessary to override the {@code hashCode} * method whenever this method is overridden, so as to maintain the * general contract for the {@code hashCode} method, which states * that equal objects must...
System.out.println("p1 and p2 are not equal"); } 在上面的代码中,我们首先创建了两个Person对象,并将它们分别存储在p1和p2引用中。接下来,我们使用equals方法比较它们的属性值是否相等,由于它们的name和age属性值相等,因此它们相等,程序将输出"p1 and p2 are equal"。 总结 在Java中,类和对象是组织和管理...
Now, if we create twoTeamobjects, both with city “New York” and department “marketing,” they will be equal, but they’ll return different hashCodes. 3.3.HashMapKey With an InconsistenthashCode() But why is the contract violation in ourTeamclass a problem? Well, the trouble starts when...
当两个对象的hashcode不同的话,肯定 他们不能equal. 改写equals时总是要改写hashCode java.lang.Object中对hashCode的约定: 1. 在一个应用程序执行期间,如果一个对象的equals方法做比较所用到的信息没有被修改的话,则对该对象调用hashCode方法多次,它必须始终如一地返回同一个整数。 2. 如果两个对象根据equals(...
这种基于值的Equal方法可以由Java类库中的所有原始封装类使用,如Integer 、Float 、 Character 和Bo 5、olean 以及String (如果两个 String 对象包含相同顺序的字符,那它们是相等的。由于这些类都 是不可修改的并且可以实施hashCode( 和equals(,它们都可以做为很好的散列关键字。为什么忽略equals(和hashCode(?如果...
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...
Java Object hashCode() is a native method and returns the integer hash code value of the object. The general contract of hashCode() method is: Multiple invocations of hashCode() should return the same integer value, unless the object property is modified that is being used in the equals() ...
* general contract for the {@code hashCode} method, which states * that equal objects must have equal hash codes. * * @param obj the reference object with which to compare. * @return {@code true} if this object is the same as the obj ...