反射

package 反射;

public class A {
   private  String a ="张三" ;
   private int m =5;

    public A(){}

    public A(String a){
        this.a = a;

    }

    public void m( ){
        System.out.println(a);
    }
}

package 反射;

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

public class test4 {
    public static void main(String[] args) {
      A a1 = new A("王二麻子");
      Class c = a1.getClass();
        try {
            Field f =c.getDeclaredField("a");   //A 中的常量名称
            f.setAccessible(true);
            String Value = f.get(a1)+" ";  //a1是new出来的对象名 通过常量名称得到常量值

            Constructor cons = c.getConstructor(String.class);  //创建调用有参获取构造方法
            A obj = (A)cons.newInstance(Value); //调用
            obj.m();

        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        }
    }
}

结果：

王二麻子

package 反射;

import java.lang.reflect.*;

public class Test3 {
    public static void main(String[]args){
        /*System.out.println(Direction.EAST);
        Direction.WEST.show();
        //判断两个枚举是否相同
        Direction dir1 = Direction.EAST;
        System.out.println(dir1 == Direction.EAST);//判断枚举是否相同的方法
        System.out.println(dir1.compareTo(Direction.WEST));//枚举下标相减 如果为0则代表两个枚举相同
        System.out.println(dir1.ordinal());//枚举下标
        System.out.println(dir1.name());//枚举字符串*/

        Class c = A.class;//类
       /* try {
            Field f = c.getField("a");
            System.out.println(f.getName());
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        }
        */
        //通过类获取里面的成员变量
        Field [] fields = c.getFields();
        for(Field f : fields){
            System.out.println(f.getName());
        }
        //获取所有方法
        //Method [] ms = c.getMethods();
        //获取当前类的方法
        /*Method [] ms = c.getDeclaredMethods();
        for(Method m : ms){
            System.out.println(m.getName());
        }*/
        //反射创建对象
        /*Object obj = null;
        try {
//            obj = c.newInstance();//调用无参构造创建对象
            //获取构造方法
           Constructor cons = c.getConstructor(String.class);
           obj = cons.newInstance("王五");
        }  catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }



        try {
           Field field = c.getDeclaredField("a");
            field.setAccessible(true);
            field.set(obj, "钱三");//设置成员变量的值
            System.out.println(field.getName());
            System.out.println(field.get(obj));//获取成员变量的值
            System.out.println(Modifier.toString(field.getModifiers()));//获取修饰符
            System.out.println(field.getType());//获取类型
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }

        try {
            Method m = c.getMethod("a",String.class,int.class);
            //执行方法
            m.invoke(obj ,"a",1);
            System.out.println(Modifier.toString(m.getModifiers()));//获取修饰符
            System.out.println(m.getReturnType());//获取返回类型
            Parameter [] ps = m.getParameters();
            for(Parameter p : ps){
                System.out.println(p.getName());//参数名
                System.out.println(p.getType());//参数类型
            }
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }*/

        try {
            Class msg = Class.forName("message.Message");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }


}