- 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：
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);
}