jvm classloader常识

jvm classloader知识

1. jvm classloader 分

bootstrap classloader

system classloader

extention classloader

 

package com.jason.jvm;

import java.net.URL;

public class JvmClassLoaderDemo {
	
	/**
	 * bootstrap classloader
	 */
	public void bootstrap(){
		URL[] urls=sun.misc.Launcher.getBootstrapClassPath().getURLs();
		for (int i = 0; i < urls.length; i++) {
			System.out.println(urls[i].toExternalForm());
		}
	}
	
	/**
	 * extention classloader
	 */
	public void extention(){
		System.out.println(System.getProperty("java.ext.dirs"));
		ClassLoader extensionClassloader=ClassLoader.getSystemClassLoader().getParent();
		System.out.println("the parent of extension classloader : "+extensionClassloader.getParent());
	}
	
	/**
	 * system classloader
	 */
	public void system(){
		System.out.println(System.getProperty("java.class.path"));
	}
	
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		JvmClassLoaderDemo a = new JvmClassLoaderDemo();
		System.out.println("**********bootstrap begin************");
		a.bootstrap();
		System.out.println("**********bootstrap end************");
		System.out.println("**********extention begin************");
		a.extention();
		System.out.println("**********extention end************");
		System.out.println("**********system begin************");
		a.system();
		System.out.println("**********system end************");

	}

}