Java instanceof和getClass()区别实例解析

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.

class Base{
  
}
class Derived extends Base{
  
}

public class Hello {
  public static void main(String[] args) throws ParseException {
    Derived d = new Derived();
    boolean bRet;
    bRet = d instanceof Derived;//true
    bRet = d instanceof Base;//true
    bRet = d.getClass() == Derived.class;//true
//   bRet = d.getClass() == Base.class;// 出错
    bRet = d.getClass().equals(Base.class);//false
  }
}

class Person{
  private String id;
  private String name;
  //重写equals()方法，提供自定义的相等标准
  public boolean equals(Object obj){
    if(this == obj)//若为同一个对象
      return true;
    //只有当obj是Person对象
    if(null != obj && obj.getClass() == Person.class){
      Person p = (Person)obj;
      if(id.equals(obj).getId() && ...){
        return true;
      }
    }
    return false;
  }
}