Type和class以及比较是相等关系

待我称王封你为后i 2022-02-01 04:47 227阅读 0赞

## 前言 ##

Type是Class的父接口。  
Class是Type的子类。

## instanceof ##

instanceof操作符用于判断一个引用类型所引用的对象是否是一个类的实例。

public  void instanceOf(Object object) { 
    
            /** * == */
            if(Long.class == object.getClass()){ 
                System.out.println("Long.class == object.getClass()");
            }
    
            /** * equals */
            if(Long.class.equals(object.getClass()) ){ 
                System.out.println("Long.class.equals(object.getClass()) ");
            }
    
            /** * instance Of */
            if(object instanceof  Long){ 
                System.out.println("object instanceof Long");
            }
        }

## == 和 equals比较的实际的Class类，没有考虑继承，instanceof 和 isInstance考虑继承 ##

class  Father{ }
    class  Son extends  Father{ }
    
    
    public void fatherAndSon(){ 
        Father son = new Son(); //和 Son son = new Son(); 一样
        Father father = new Father();
    
        //son.getClass() == father.getClass() :false
        System.out.println("son.getClass() == father.getClass() :" +(son.getClass() == father.getClass()) );
    
        //son.getClass().equals(father.getClass()) :false
        System.out.println("son.getClass().equals(father.getClass()) :" +(son.getClass().equals(father.getClass())) );
    
        //son instanceof Father :true
        System.out.println("son instanceof Father :" +(son  instanceof Father ));
    
        //father instanceof Son :false //父类不能 instanceof 子类
        System.out.println("father instanceof Son :" +(father  instanceof Son ));
    
        //father instanceof Father :true
        System.out.println("father instanceof Father :" +(father  instanceof Father ));
    
        //son.getClass().isInstance(father):false //子类不能 isInstance 父亲
      System.out.println("son.getClass().isInstance(father):"+son.getClass().isInstance(father));
    
        //father.getClass().isInstance(son):true
      System.out.println("father.getClass().isInstance(son):"+father.getClass().isInstance(son));
    
        //son.getClass().isInstance(son)true
      System.out.println("son.getClass().isInstance(son)"+son.getClass().isInstance(son));
    
    }
    
    @Test
    public void testFatherAndSon(){ 
        fatherAndSon();
    }

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