Main.java Source code

Introduction

Here is the source code for Main.java

Source

/* Copyright (c) 2011.  Peter Lawrey
 *
 * "THE BEER-WARE LICENSE" (Revision 128)
 * As long as you retain this notice you can do whatever you want with this stuff.
 * If we meet some day, and you think this stuff is worth it, you can buy me a beer in return
 * There is no warranty.
 */

import java.lang.reflect.Field;
import java.net.URL;
import java.net.URLClassLoader;

public class Main {
    public static void main(String... args)
            throws ClassNotFoundException, NoSuchFieldException, IllegalAccessException, InterruptedException {
        URL url = Main.class.getProtectionDomain().getCodeSource().getLocation();
        final String className = Main.class.getPackage().getName() + ".UtilityClass";
        {
            ClassLoader cl;
            Class clazz;

            for (int i = 0; i < 2; i++) {
                cl = new CustomClassLoader(url);
                clazz = cl.loadClass(className);
                loadClass(clazz);

                cl = new CustomClassLoader(url);
                clazz = cl.loadClass(className);
                loadClass(clazz);
                triggerGC();
            }
        }
        triggerGC();
    }

    private static void triggerGC() throws InterruptedException {
        System.out.println("\n-- Starting GC");
        System.gc();
        Thread.sleep(100);
        System.out.println("-- End of GC\n");
    }

    private static void loadClass(Class clazz) throws NoSuchFieldException, IllegalAccessException {
        final Field id = clazz.getDeclaredField("ID");
        id.setAccessible(true);
        id.get(null);
    }

    private static class CustomClassLoader extends URLClassLoader {
        public CustomClassLoader(URL url) {
            super(new URL[] { url }, null);
        }

        @Override
        protected Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException {
            try {
                return super.loadClass(name, resolve);
            } catch (ClassNotFoundException e) {
                return Class.forName(name, resolve, Main.class.getClassLoader());
            }
        }

        @Override
        protected void finalize() throws Throwable {
            super.finalize();
            System.out.println(this.toString() + " - CL Finalized.");
        }
    }
}

class UtilityClass {
    static final String ID = Integer.toHexString(System.identityHashCode(UtilityClass.class));
    private static final Object FINAL = new Object() {
        @Override
        protected void finalize() throws Throwable {
            super.finalize();
            System.out.println(ID + " Finalized.");
        }
    };

    static {
        System.out.println(ID + " Initialising");
    }
}