Java example source code file (Basic.java)

This example Java source code file (Basic.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

address_size, class, compressedoopsclass, contended, exception, field, header_size, management, nosuchfieldexception, object, reflection, regex, string, test5, test7, test9, threading, threads, unsafe, util

The Basic.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.BufferedReader;
import java.io.InputStreamReader;
import java.lang.Class;
import java.lang.String;
import java.lang.System;
import java.lang.management.ManagementFactory;
import java.lang.management.RuntimeMXBean;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CyclicBarrier;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import sun.misc.Unsafe;
import sun.misc.Contended;

/*
 * @test
 * @bug     8003985
 * @summary Support Contended Annotation - JEP 142
 *
 * @run main/othervm -XX:-RestrictContended Basic
 */
public class Basic {

    private static final Unsafe U;
    private static int ADDRESS_SIZE;
    private static int HEADER_SIZE;

    static {
        // steal Unsafe
        try {
            Field unsafe = Unsafe.class.getDeclaredField("theUnsafe");
            unsafe.setAccessible(true);
            U = (Unsafe) unsafe.get(null);
        } catch (NoSuchFieldException | IllegalAccessException e) {
            throw new IllegalStateException(e);
        }

        // When running with CompressedOops on 64-bit platform, the address size
        // reported by Unsafe is still 8, while the real reference fields are 4 bytes long.
        // Try to guess the reference field size with this naive trick.
        try {
            long off1 = U.objectFieldOffset(CompressedOopsClass.class.getField("obj1"));
            long off2 = U.objectFieldOffset(CompressedOopsClass.class.getField("obj2"));
            ADDRESS_SIZE = (int) Math.abs(off2 - off1);
            HEADER_SIZE = (int) Math.min(off1, off2);
        } catch (NoSuchFieldException e) {
            ADDRESS_SIZE = -1;
        }
    }

    static class CompressedOopsClass {
        public Object obj1;
        public Object obj2;
    }

    public static boolean arePaddedPairwise(Class klass, String field1, String field2) throws Exception {
        Field f1 = klass.getDeclaredField(field1);
        Field f2 = klass.getDeclaredField(field2);

        if (isStatic(f1) != isStatic(f2)) {
            return true; // these guys are in naturally disjoint locations
        }

        int diff = offset(f1) - offset(f2);
        if (diff < 0) {
            // f1 is first
            return (offset(f2) - (offset(f1) + getSize(f1))) > 64;
        } else {
            // f2 is first
            return (offset(f1) - (offset(f2) + getSize(f2))) > 64;
        }
    }

    public static boolean isPadded(Class klass, String field1) throws Exception {
        Field f1 = klass.getDeclaredField(field1);

        if (isStatic(f1)) {
            return offset(f1) > 128 + 64;
        }

        return offset(f1) > 64;
    }

    public static boolean sameLayout(Class klass1, Class klass2) throws Exception {
        for (Field f1 : klass1.getDeclaredFields()) {
            Field f2 = klass2.getDeclaredField(f1.getName());
            if (offset(f1) != offset(f2)) {
                return false;
            }
        }

        for (Field f2 : klass1.getDeclaredFields()) {
            Field f1 = klass2.getDeclaredField(f2.getName());
            if (offset(f1) != offset(f2)) {
                return false;
            }
        }

        return true;
    }

    public static boolean isStatic(Field field) {
        return Modifier.isStatic(field.getModifiers());
    }

    public static int offset(Field field) {
        if (isStatic(field)) {
            return (int) U.staticFieldOffset(field);
        } else {
            return (int) U.objectFieldOffset(field);
        }
    }

    public static int getSize(Field field) {
        Class type = field.getType();
        if (type == byte.class)    { return 1; }
        if (type == boolean.class) { return 1; }
        if (type == short.class)   { return 2; }
        if (type == char.class)    { return 2; }
        if (type == int.class)     { return 4; }
        if (type == float.class)   { return 4; }
        if (type == long.class)    { return 8; }
        if (type == double.class)  { return 8; }
        return ADDRESS_SIZE;
    }

    public static void main(String[] args) throws Exception {
        boolean endResult = true;

        // --------------- INSTANCE FIELDS ---------------------

        if (arePaddedPairwise(Test1.class, "int1", "int2") ||
                isPadded(Test1.class, "int1") ||
                isPadded(Test1.class, "int2")) {
            System.err.println("Test1 failed");
            endResult &= false;
        }

        if (!arePaddedPairwise(Test2.class, "int1", "int2") ||
                !isPadded(Test2.class, "int1") ||
                isPadded(Test2.class, "int2")) {
            System.err.println("Test2 failed");
            endResult &= false;
        }

        if (!arePaddedPairwise(Test3.class, "int1", "int2") ||
                !isPadded(Test3.class, "int1") ||
                !isPadded(Test3.class, "int2")) {
            System.err.println("Test3 failed");
            endResult &= false;
        }

        if (arePaddedPairwise(Test4.class, "int1", "int2") ||
                !isPadded(Test4.class, "int1") ||
                !isPadded(Test4.class, "int2")) {
            System.err.println("Test4 failed");
            endResult &= false;
        }

        if (!arePaddedPairwise(Test5.class, "int1", "int2") ||
                !isPadded(Test5.class, "int1") ||
                !isPadded(Test5.class, "int2")) {
            System.err.println("Test5 failed");
            endResult &= false;
        }

        if (!arePaddedPairwise(Test6.class, "int1", "int2") ||
                !isPadded(Test6.class, "int1") ||
                !isPadded(Test6.class, "int2")) {
            System.err.println("Test6 failed");
            endResult &= false;
        }

        if (arePaddedPairwise(Test7.class, "int1", "int2") ||
                !isPadded(Test7.class, "int1") ||
                !isPadded(Test7.class, "int2")) {
            System.err.println("Test7 failed");
            endResult &= false;
        }

        if (!arePaddedPairwise(Test8.class, "int1", "int2") ||
                !isPadded(Test8.class, "int1") ||
                !isPadded(Test8.class, "int2")) {
            System.err.println("Test8 failed");
            endResult &= false;
        }

        if (!arePaddedPairwise(Test9.class, "int1", "int2") ||
                !isPadded(Test9.class, "int1") ||
                !isPadded(Test9.class, "int2")) {
            System.err.println("Test9 failed");
            endResult &= false;
        }

        if (!sameLayout(Test4.class, Test7.class)) {
            System.err.println("Test4 and Test7 have different layouts");
            endResult &= false;
        }

        if (!sameLayout(Test5.class, Test6.class)) {
            System.err.println("Test5 and Test6 have different layouts");
            endResult &= false;
        }

        if (!sameLayout(Test8.class, Test9.class)) {
            System.err.println("Test8 and Test9 have different layouts");
            endResult &= false;
        }

        System.out.println(endResult ? "Test PASSES" : "Test FAILS");
        if (!endResult) {
           throw new Error("Test failed");
        }
    }

    // ----------------------------------- INSTANCE FIELDS -----------------------------------------

    // naturally packed
    public static class Test1 {
                                 private int int1;
                                 private int int2;
    }

    // int1 is padded
    public static class Test2 {
        @Contended               private int int1;
                                 private int int2;
    }

    // both fields are padded
    public static class Test3 {
        @Contended               private int int1;
        @Contended               private int int2;
    }

    // fields are padded in the singular group
    public static class Test4 {
        @Contended("sameGroup")  private int int1;
        @Contended("sameGroup")  private int int2;
    }

    // fields are padded in disjoint groups
    public static class Test5 {
        @Contended("diffGroup1") private int int1;
        @Contended("diffGroup2") private int int2;
    }

    // fields are padded in disjoint groups
    public static class Test6 {
        @Contended               private int int1;
        @Contended("diffGroup2") private int int2;
    }

    // fields are padded in the singular group
    @Contended
    public static class Test7 {
                                 private int int1;
                                 private int int2;
    }

    // all fields are padded as the group, and one field is padded specifically
    @Contended
    public static class Test8 {
        @Contended               private int int1;
                                 private int int2;
    }

    // all fields are padded as the group, and one field is padded specifically
    @Contended
    public static class Test9 {
        @Contended("group")      private int int1;
                                 private int int2;
    }

}