isInstance和isAssignableFrom的用法

        String str = "";
        Object o = new Object();
        System.out.println(String.class.isInstance(o));
        System.out.println(Object.class.isInstance(o));
        System.out.println(Object.class.isInstance(str));

        System.out.println(String.class.isAssignableFrom(Object.class));
        System.out.println(Object.class.isAssignableFrom(Object.class));
        System.out.println(Object.class.isAssignableFrom(String.class));

output:

false
true
true
false
true
true