java - 如何调用 "toString"的默认实现？

Question

如果未定义 toString，则 Java 会打印带有一些散列的类名。如果定义了 toString，如何实现此功能？

package tests.java.lang;

public class Try_ToString {

    public static class MyClass {

        protected int value;

        public MyClass(int value) {
            this.value = value;
        }
    }

    public static class MyClass2 extends MyClass {
        public MyClass2(int value) {
            super(value);
        }
        @Override
        public String toString() {
            return String.valueOf(value);
        }
    }

    public static void main(String[] args) {

        MyClass a = new MyClass(12);
        MyClass b = new MyClass2(12);

        System.out.println("a = " + a.toString());
        System.out.println("b = " + b.toString());

    }
}

Answer 1

@immibis 的回答是正确的，但是如果你的类重写 hashcode 方法，它就不会工作。但是你可以使用 System.identityHashcode .

Returns the same hash code for the given object as would be returned by the default method hashCode(), whether or not the given object's class overrides hashCode(). The hash code for the null reference is zero.

public static String defaultToString(Object o) {
     return o.getClass().getName() + "@" + 
            Integer.toHexString(System.identityHashCode(o));
}