如何在java中使用反射来调用类的公共成员中的方法

Question

A类:

public class A {
    public B b;
    public A(String s) {
        b = new B(s);
    }
}

B类:

public class B {
    String s;
    public B(String s) {
        this.s = s;
    }
    public void printB() {
        System.out.println(this.s);
    }
}

所以我想在java中使用反射来创建类A，并使用他的公共成员B来运行printB方法，使用反射从客户端'printB'给定字符串

我该怎么做?

Answer 1

我不知道你为什么想要，但是作为概念的证明…

package myPackage;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
public class Test {
    public static void main(String[] args) {
        try {
            Class clazz = Class.forName("myPackage.Test$a");
            Constructor con = clazz.getConstructor(String.class);
            Object instanceOfA = con.newInstance("A value");
            Field bField = clazz.getField("b");
            Object instanceOfB = bField.get(instanceOfA);
            Method printBMethod = instanceOfB.getClass().getMethod("printB");
            printBMethod.invoke(instanceOfB);
        } catch (ClassNotFoundException | NoSuchMethodException | SecurityException | InstantiationException | IllegalAccessException | IllegalArgumentException | InvocationTargetException | NoSuchFieldException ex) {
            ex.printStackTrace();
        }
    }
    public static class a {
        public B b;
        public a(String s) {
            b = new B(s);
        }
    }
    public static class B {
        String s;
        public B(String s) {
            this.s = s;
        }
        public void printB() {
            System.out.println(this.s);
        }
    }
}