Java 反射机制 练习代码

//TesDynamicLoading.java


public class TestDynamicLoading {

	public static void main(String[] args) {
		new A();
		System.out.println("********************************************");
		new B();
		
		new C();
		new C();
		
		new D(1);
		new D(1);
	}

}

class A{
	
}

class B{
	
}

class C{
	static{//类加载时被执行
		System.out.println("CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC");
	}
}

class D{
	D(int i){
		
	}
	{//为对象分配内存时执行
		System.out.println("DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD");
	}
}

//TestJDKClassloader.java


public class TestJDKClassLoader {

	public static void main(String[] args) {
		/*System.out.println(String.class.getClassLoader());
		System.out.println(com.sun.crypto.provider.DESKeyFactory.class
				.getClassLoader().getClass().getName());
		System.out.println(TestJDKClassLoader.class.getClassLoader().getClass()
				.getName());
		System.out.println(ClassLoader.getSystemClassLoader().getClass().getName());*/
		
		ClassLoader c=TestJDKClassLoader.class.getClassLoader();
		while(c!=null){
			System.out.println(c.getClass().getName());
			c=c.getParent();
		}
		
		
	}

}

//TestReflection.java

import java.lang.reflect.Method;

public class TestReflection {

	public static void main(String[] args) throws Exception {
		String str = "T";
		Class c = Class.forName(str);
		Object o = c.newInstance();
		Method[] methods = c.getMethods();
		for (Method m : methods) {
			if (m.getName().equals("mm")) {
				m.invoke(o, new Object[] {});
			}
			if (m.getName().equals("m1")) {
				m.invoke(o, 1, 2);
				for(Class parameterTypes:m.getParameterTypes()){
					System.out.println(parameterTypes.getName());
				}
			}
			if(m.getName().equals("getS")){
				Class returnType = m.getReturnType();
				System.out.println(returnType.getName());
			}
		}
	}

}

class T {
	static {
		System.out.println("T is Loading !");
	}

	public T() {
		System.out.println("Constructor Called !");
	}

	int i;
	String s;

	public void mm() {
		System.out.println("m invoked !");
	}

	public void m1(int i, int j) {
		this.i = i + j;
		System.out.println(" i = " + this.i);
	}

	public String getS() {
		return s;
	}
}