student物件

package MaReflection;

public class Student {
	private int num;
	private String name;
	static {
		System.out.println("[執行靜態區塊]");
	}

	public int getNum() {
		return num;
	}

	public void setNum(int num) {
		this.num = num;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public static void talk(String dd) {
		System.out.println("學生說話了");
		System.out.println(dd);
	}

	@Override
	public String toString() {
		return "Student [num=" + num + ", name=" + name + "]";
	}
	
}
 

主類

package MaReflection;

import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

public class MaRelectionStudent {
	public static void main(String[] args) throws Exception{
     updateStudent("MaReflection.Student", "name", "num", "talk");
	}
	
	public static void updateStudent(String className,String namefield,String numfiled,String methodname) throws NoSuchMethodException, SecurityException, ClassNotFoundException, InstantiationException, IllegalAccessException, NoSuchFieldException, IllegalArgumentException, InvocationTargetException {
		Class clazz = Class.forName(className);
		Object o = clazz.newInstance();
		System.out.println(o.toString());
		
		Field field_name = clazz.getDeclaredField(namefield);
		field_name.setAccessible(true);//這個是修改物件屬性必須設定的，不然set屬性會報錯,因為這個物件屬性為private
		field_name.set(o, "張三");
		
		Field field_num = clazz.getDeclaredField(numfiled);
		field_num.setAccessible(true);
		field_num.setInt(o, 1);
		
		Method method = clazz.getDeclaredMethod(methodname,String.class);//methodname是方法名     String.class這個是傳入引數方法型別
		method.setAccessible(true);
		System.out.println("method.getName()++++"+method.getName());
		System.out.println("method.getParameterTypes()+++"+method.getParameterTypes());
		System.out.println(o.toString());
		System.out.println("+++++++++++++++");
		Object fObject=method.invoke(o,"我就是方法的引數");
	    System.out.println(fObject);
	}
}
 

執行結果：

[執行靜態區塊]
Student [num=0, name=null]
method.getName()++++talk
method.getParameterTypes()+++[Ljava.lang.Class;@6d06d69c
Student [num=1, name=張三]
+++++++++++++++
學生說話了
我就是方法的引數
null

利用java反射可以對，物件的私有屬性和方法就行呼叫和動態修改。