Java.lang.object has two very important methods defined: public boolean equals(Object obj) and public int hashCode().equals() methodIn java equals() method is used to compare equality of two Objects. The equality can be compared in two ways:...
HashMap, Hashtable, or WeakHashMap, make sure that the hashCode() of the key objects that you put into the collection never changes while the object is in the collection. The bulletproof way to ensure this is to make your keys immutable, which has also other benefits. ...
Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified. This integer need not remain consistent from one executio...
* method, then calling the {@code hashCode} method on each of * the two objects must produce the same integer result. * It is not required that if two objects are unequal * according to the {@link java.lang.Object#equals(java.lang.Object)} * method, then calling the {@code hashCode...
1.2hashCode()方法 这个方法是Object类的一个原生方法,它返回一个整数,代表这个对象的Hash值。 如果要自定义覆盖实现这个方法,需要注意遵守: Multiple invocations of hashCode() should return the same integer value, unless the object property is modified that is being used in the equals() method. ...
最后,补充一点,Sun公司Object的equals方法文档上指明:for any non-null reference values x and y, this method returns true if and only if x and y refer to the same object (x == y has the value true). Note that it is generally necessary tooverride the hashCode method whenever this method ...
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() ...
Whenevera.equals(b), thena.hashCode()must be same asb.hashCode(). If we override one method, then we should override the other method as well. 6. Special Attention When Declared in an JPA Entity If you’re dealing with an ORM, make sure always to use gettersand never use the field ...
在JavaSE 7 Specification中指出, "Note that it is generally necessary to override the hashCode method whenever this method(equals) is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes." ...
下文解释了为什么需要这种方法的复杂原因:How to Write an Equality Method in Java。如果层次结构中的所有类都是scala case类和带有lombok生成的equals方法的类的混合,则所有的相等都能正常工作。如果你需要编写自己的equals方法,那么如果更改equals和hashCode方法,都应该始终覆盖canEqual....