class A { }

class B extends A { }

Object o1 = new A();

Object o2 = new B();

o1 instanceof A => true

o1 instanceof B => false

o2 instanceof A => true // <================ HERE

o2 instanceof B => true

o1.getClass().equals(A.class) => true

o1.getClass().equals(B.class) => false

o2.getClass().equals(A.class) => false // <===============HERE

o2.getClass().equals(B.class) => true

getClass() will be useful when you want to make sure your instance is NOT a subclass of the class you are comparing with.

一个非常完美的equals方法的写法：

复制代码 代码如下:

public boolean equals(Object otherObject)

{

// a quick test to see if the objects are identical

if (this == otherObject) return true;

// must return false if the explicit parameter is null

if (otherObject == null) return false;

// if the classes don't match, they can't be equal

if (getClass() != otherObject.getClass()) return false;

// now we know otherObject is a non-null Employee

Employee other = (Employee) otherObject;

// test whether the fields have identical values

return name.equals(other.name) && salary == other.salary && hireDay.equals(other.hireDay);

}