对象在不重写的情况下使用的是Object的equals方法和hashcode方法,从Object类的源码我们知道,默认的equals 判断的是两个对象的引用指向的是不是同一个对象;而hashcode也是根据对象地址生成一个整数数值; 另外我们可以看到Object的hashcode()方法的修饰符为native,表明该方法是否操作系统实现,java调用操作系统底层代码获取哈希...
The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, 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 ...
publicclassTest{privateStringname;privateintcode;publicTest(Stringname,intcode){this.name=name;this.code=code;}publicTest(){}@Overridepublicbooleanequals(Objecto){if(this==o)returntrue;if(o==null||getClass()!=o.getClass())returnfalse;Testtest=(Test)o;returncode==test.code&&Objects.equals(na...
In which case will I face a problem if I haven't overridden the hashCode method? A: The problem you will have is with collections where unicity of elements is calculated according to both.equals()and.hashCode(), for instance keys in aHashMap. As its name implies, it relies on hash tab...
String is actually a subclass of Object and its equals method is overridden, making it work on Strings like hello1 and hello3 from Example 1 as expected. User classes @Test public void porscheShouldBeEqual() { Car myPorsche1 = new Car("Marcus", "Porsche", "silver"); ...
public boolean equals(Object obj) { // TODO Auto-generated method stub //如果是自己 if(this==obj){ return true ; } //如果是空 if(obj==null ){ return false; } //比较两个People的名字是否相同 if(obj!=null && obj instanceof People){ ...
Add this method to theEmployeeclass, andEqualsTestwill start returning"true". So are we done? Not yet. Let’s test the above-modifiedEmployeeclass again in a different way. importjava.util.HashSet;importjava.util.Set;publicclassEqualsTest{publicstaticvoidmain(String[]args){Employeee1=newEmploye...
本文介绍一下几种重写equals和hashcode的方法。 规则 如果两个对象相等的话,它们的hash code必须相等; 但如果两个对象的hash code相等的话,这两个对象不一定相等。 方法 使用lombok的注解 lombok-1.16.16.jar!/lombok/EqualsAndHashCode.class 比如 代码语言:javascript ...
"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." ...
Ifo1.equals(o2), theno1.hashCode() == o2.hashCode()should always betrue. Ifo1.hashCode() == o2.hashCodewill be. When to override equals() and hashCode() methods? When we override equals() method, it’s almost necessary to override the hashCode() method too so that their contract is...