jdk6.0从入门到精通-----chapter16反射机制

反射机制用到java.lang.reflect包中的类
一下是一个小例子：

package example1;

import java.lang.reflect.Method;

public class PrintMethods {
	public static void main(String[] args) throws Exception {
		// 加载并初始化命令行参数指定的类
		Class classType = Class.forName(args[0]); // 一定是类的全名字，加上package，如java.lang.Object
		Method methods[] = classType.getDeclaredMethods(); // 获得类的所有方法
		for (int i = 0; i < methods.length; i++) {
			System.out.println(methods[i].toString());
		}
	}

}

如果参数是：java.lang.Object
执行结果 

protected void java.lang.Object.finalize() throws java.lang.Throwable
 public final void java.lang.Object.wait() throws
 java.lang.InterruptedException
 public final void java.lang.Object.wait(long,int) throws
 java.lang.InterruptedException
 public final native void java.lang.Object.wait(long) throws
 java.lang.InterruptedException
 public native int java.lang.Object.hashCode()
 public final native java.lang.Class java.lang.Object.getClass()
 protected native java.lang.Object java.lang.Object.clone() throws
 java.lang.CloneNotSupportedException
 private static native void java.lang.Object.registerNatives()
 public boolean java.lang.Object.equals(java.lang.Object)
 public java.lang.String java.lang.Object.toString()
 public final native void java.lang.Object.notify()
 public final native void java.lang.Object.notifyAll()

第二个例子；

对象接口：

package example2;
public interface ObjInterface {

	public String getGreeting();
}

对象实体类

package example2;
public class ObjImpl implements ObjInterface {

	@Override
	//内置的java的Annotation类型@Override
	public String getGreeting() {
		return "hello world!";
	}

}

测试类：

package example2;

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

public class Main {

	public static void main(String[] args) throws ClassNotFoundException,
			InstantiationException, IllegalAccessException, SecurityException,
			NoSuchMethodException, IllegalArgumentException,
			InvocationTargetException {
		// 根据类名称创建类实例
		Class objClass = Class.forName("example2.ObjImpl"); // ClassNotFoundException
		// 面向接口
		ObjInterface obj = (ObjInterface) objClass.newInstance();// InstantiationException,IllegalAccessException
		// ObjImpl obj = (ObjImpl) objClass.newInstance(); //这样也可

		System.out.println(obj.getGreeting());

		// 根据方法名称创建方法实例
		Method method = obj.getClass().getMethod("getGreeting", // 错错？？？？？？NoSuchMethodException？？？
				new Class[] { String.class });// SecurityException,
		// NoSuchMethodException

		// 动态调用方法
		Object result = method.invoke(obj, new Object[] { "Tu chuanbin" }); // InvocationTargetException
		System.out.println("返回结果：" + (String) result);

	}

}