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  • instanceof、isInstance、isAssignableFrom的区别

    https://stackoverflow.com/questions/3949260/java-class-isinstance-vs-class-isassignablefrom

    1. MyClass.class.isInstance(obj) is for checking an instance. It returns true when the parameter obj is non-null and can be cast to MyClass without raising a ClassCastException. In other words, obj is an instance of MyClass or its subclasses.

    2. MyClass.class.isAssignableFrom(Other.class) will return true if MyClass is the same as, or a superclass or superinterface of, OtherOther can be a class or an interface. It answers true if Other can be converted to a MyClass.

    public class NewMain
    {
        public static void main(String[] args)
        {
            NewMain nm = new NewMain();
            nm.doit();
        }
    
        public void doit()
        {
            A myA = new A();
            B myB = new B();
            A[] aArr = new A[0];
            B[] bArr = new B[0];
    
            System.out.println("b instanceof a: " + (myB instanceof A));
            System.out.println("b isInstance a: " + A.class.isInstance(myB));
            System.out.println("a isInstance b: " + B.class.isInstance(myA));
            System.out.println("b isAssignableFrom a: " + A.class.isAssignableFrom(B.class));
            System.out.println("a isAssignableFrom b: " + B.class.isAssignableFrom(A.class));
            System.out.println("bArr isInstance A: " + A.class.isInstance(bArr));
            System.out.println("bArr isInstance aArr: " + aArr.getClass().isInstance(bArr));
            System.out.println("bArr isAssignableFrom aArr: " + aArr.getClass().isAssignableFrom(bArr.getClass()));
        }
    
        class A
        {
        }
    
        class B extends A
        {
        }
    }

    结果

    b instanceof a: true
    b isInstance a: true
    a isInstance b: false
    b isAssignableFrom a: true
    a isAssignableFrom b: false
    bArr isInstance A: false
    bArr isInstance aArr: true
    bArr isAssignableFrom aArr: true
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  • 原文地址:https://www.cnblogs.com/davidwang456/p/8350173.html
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