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  • java 判断类和实例的关系(instanceof,isInstance,isAssignableFrom)

    判断类与实例的关系有以下三种方式 

    1、instanceOf关键字,用来判断对象是否是类的实例 
    2、isAssignableFrom,用来判断类型间是否存在派生关系 
    3、isInstance方法,用来判断对象是否属于某个类型的实例 

     

            //use instanceOf,用来判断对象是否是类的实例
            System.out.println(new A() instanceof B);//类型比较
    
            //use isAssignableFrom(),用来判断类型间是否有继承关系
    
            System.out.println(B.class.isAssignableFrom(A.class));
     
            //use isInstance(),用来判断对象是否是类的实例
    
            System.out.println(A.class.isInstance(new A()));//class比较
    import java.util.Date;
    
    public class Program
    {
        public static void main(String[] args)
        {
            // Get the Class object associated with Integer.
            Class intClass = Integer.class;
    
            // Create various objects.
            String str = "Hello";
            Date date = new Date();
            Integer i = new Integer(10);
    
            // Is str an instance of class Integer?
            boolean check1 = intClass.isInstance(str);
            System.out.println("str is an Integer? " + check1);
    
            // Is date an instance of class Integer?
            boolean check2 = intClass.isInstance(date);
            System.out.println("date is an Integer? " + check2);
    
            // Is i an instance of class Integer?
            boolean check3 = intClass.isInstance(i);
            System.out.println("i is an Integer? " + check3);
        }
    }
    
    /*
    Output:
    str is an Integer? false
    date is an Integer? false
    i is an Integer? true
    */

     

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  • 原文地址:https://www.cnblogs.com/feiling/p/2490661.html
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