Java反射 基础

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
class ReflectPoint {
	private int x;
	public int y;
	public ReflectPoint(int x, int y) {
		super();
		this.x = x;
		this.y = y;
	}
	
}
public class Test {
	public static void main(String[] args) throws Exception {
		//Class类
		String str1 = "abc";
		Class cls1 = Class.forName("java.lang.String");
		Class cls2 = String.class;
		Class cls3 = str1.getClass();
		System.out.println(cls1 == cls2); //true
		System.out.println(cls2 == cls3); //true
		System.out.println(int.class.isPrimitive()); //基本类型, true
		System.out.println(int.class == Integer.TYPE); //Integer对应的基本类型字节码, true
		System.out.println("---------");
		
		//构造函数的反射
		Constructor constructor1 = cls1.getDeclaredConstructor(String.class);
		String str2 = (String) constructor1.newInstance(new String("ccc"));
		System.out.println(str2);
		System.out.println("---------");
		
		//成员变量的反射
		ReflectPoint pt1 = new ReflectPoint(3, 5);
		Field fieldY = pt1.getClass().getField("y"); //getField要是共有的字段，fieldY是字节码
		System.out.println(fieldY.get(pt1));
		
		Field fieldX = pt1.getClass().getDeclaredField("x"); //getDeclaredField所有声明的都有
		fieldX.setAccessible(true);  //暴力反射
		System.out.println(fieldX.get(pt1));
		System.out.println("---------");
		
		//函数方法的反射
		String str3 = "xyz123";
		Method methodCharAt = String.class.getMethod("charAt", int.class);
		System.out.println(methodCharAt.invoke(str3, 1));
		System.out.println("---------");
	}

}
/*输出
true
true
 */