Java example source code file (ClassUnloadCommon.java)

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Java - Java tags/keywords

arraylist, classunloadcommon, malformedurlexception, net, network, object, runtimeexception, string, testfailure, unexpected, url, urlclassloader, util

The ClassUnloadCommon.java Java example source code

/*
 * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

import java.io.File;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;
import java.nio.file.Paths;
import java.util.ArrayList;

public class ClassUnloadCommon {
    public static class TestFailure extends RuntimeException {
        TestFailure(String msg) {
            super(msg);
        }
    }

    public static void failIf(boolean value, String msg) {
        if (value) throw new TestFailure("Test failed: " + msg);
    }

    private static volatile Object dummy = null;
    private static void allocateMemory(int kilobytes) {
        ArrayList<byte[]> l = new ArrayList<>();
        dummy = l;
        for (int i = kilobytes; i > 0; i -= 1) {
            l.add(new byte[1024]);
        }
        l = null;
        dummy = null;
    }

    public static void triggerUnloading() {
        allocateMemory(16 * 1024); // yg size is 8m with cms, force young collection
        System.gc();
    }

    public static ClassLoader newClassLoader() {
        try {
            return new URLClassLoader(new URL[] {
                Paths.get(System.getProperty("test.classes",".") + File.separatorChar + "classes").toUri().toURL(),
            }, null);
        } catch (MalformedURLException e){
            throw new RuntimeException("Unexpected URL conversion failure", e);
        }
    }

}