Java example source code file (MemoryTest.java)

This example Java source code file (MemoryTest.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

exception, expected, failed, integer, listiterator, management, memorymanagermxbean, memorypoolmxbean, memorytype, nonheap, num_types, number, runtimeexception, string, test, util

The MemoryTest.java Java example source code

/*
 * Copyright (c) 2003, 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.
 */

/*
 * @test
 * @bug     4530538
 * @summary Basic unit test of MemoryMXBean.getMemoryPools() and
 *          MemoryMXBean.getMemoryManager().
 * @author  Mandy Chung
 *
 * @run main MemoryTest 2
 */

/*
 * NOTE: This expected result is hardcoded in this test and this test
 *       will be affected if the heap memory layout is changed in
 *       the future implementation.
 */

import java.lang.management.*;
import java.util.*;

public class MemoryTest {
    private static boolean testFailed = false;
    private static MemoryMXBean mm = ManagementFactory.getMemoryMXBean();
    private static final int HEAP = 0;
    private static final int NONHEAP = 1;
    private static final int NUM_TYPES = 2;

    // WARNING: if the number of pools changes in the future,
    // this test needs to be modified to handle different version of VMs.

    // Hotspot VM 1.5 expected to have
    //   heap memory pools     = 3 (Eden, Survivor spaces, Old gen)
    //   non-heap memory pools = 2 (Perm gen, Code cache)
    //                           or 4 if Class Sharing is enabled.
    // Number of memory managers = 3
    // They are: Copy/Scavenger + MSC + CodeCache manager
    // (or equivalent for other collectors)
    // Number of GC memory managers = 2

    // Hotspot VM 1.8+ after perm gen removal is expected to have two or
    // three non-heap memory pools:
    // - Code cache
    // - Metaspace
    // - Compressed Class Space (if compressed class pointers are used)
    private static int[] expectedMinNumPools = {3, 2};
    private static int[] expectedMaxNumPools = {3, 3};
    private static int expectedNumGCMgrs = 2;
    private static int expectedNumMgrs = expectedNumGCMgrs + 2;
    private static String[] types = { "heap", "non-heap" };

    public static void main(String args[]) throws Exception {
        Integer value = new Integer(args[0]);
        expectedNumGCMgrs = value.intValue();
        expectedNumMgrs = expectedNumGCMgrs + 2;

        checkMemoryPools();
        checkMemoryManagers();
        if (testFailed)
            throw new RuntimeException("TEST FAILED.");

        System.out.println("Test passed.");

    }

    private static void checkMemoryPools() throws Exception {
        List pools = ManagementFactory.getMemoryPoolMXBeans();
        boolean hasPerm = false;

        int[] numPools = new int[NUM_TYPES];
        for (ListIterator iter = pools.listIterator(); iter.hasNext();) {
            MemoryPoolMXBean pool = (MemoryPoolMXBean) iter.next();
            if (pool.getType() == MemoryType.HEAP) {
                numPools[HEAP]++;
            }
            if (pool.getType() == MemoryType.NON_HEAP) {
                numPools[NONHEAP]++;
            }
            if (pool.getName().toLowerCase().contains("perm")) {
                hasPerm = true;
            }
        }

        if (hasPerm) {
            // If the VM has perm gen there will be between 2 and 4 non heap
            // pools (4 if class data sharing is used)
            expectedMinNumPools[NONHEAP] = 2;
            expectedMaxNumPools[NONHEAP] = 4;
        }

        // Check the number of Memory pools
        for (int i = 0; i < NUM_TYPES; i++) {
            if (numPools[i] < expectedMinNumPools[i] ||
                    numPools[i] > expectedMaxNumPools[i]) {
                throw new RuntimeException("TEST FAILED: " +
                    "Number of " + types[i] + " pools = " + numPools[i] +
                    " but expected <= " + expectedMaxNumPools[i] +
                    " and >= " + expectedMinNumPools[i]);
            }
        }
    }

    private static void checkMemoryManagers() throws Exception {
        List mgrs = ManagementFactory.getMemoryManagerMXBeans();

        int numGCMgr = 0;

        // Check the number of Memory Managers
        for (ListIterator iter = mgrs.listIterator(); iter.hasNext();) {
            MemoryManagerMXBean mgr = (MemoryManagerMXBean) iter.next();
            String[] poolNames = mgr.getMemoryPoolNames();
            if (poolNames == null || poolNames.length == 0) {
                throw new RuntimeException("TEST FAILED: " +
                    "Expected to have one or more pools for " +
                    mgr.getName() + "manager.");
            }

            if (mgr instanceof GarbageCollectorMXBean) {
                numGCMgr++;
            } else {
                for (int i = 0; i < poolNames.length; i++) {
                    checkPoolType(poolNames[i], MemoryType.NON_HEAP);
                }
            }
        }

        if (mgrs.size() != expectedNumMgrs) {
            throw new RuntimeException("TEST FAILED: " +
                "Number of memory managers = " + mgrs.size() +
                " but expected = " + expectedNumMgrs);
        }
        if (numGCMgr != expectedNumGCMgrs) {
            throw new RuntimeException("TEST FAILED: " +
                "Number of GC managers = " + numGCMgr + " but expected = " +
                expectedNumGCMgrs);
        }
    }
    private static List pools = ManagementFactory.getMemoryPoolMXBeans();
    private static void checkPoolType(String name, MemoryType type)
        throws Exception {
        for (ListIterator iter = pools.listIterator(); iter.hasNext(); ) {
            MemoryPoolMXBean pool = (MemoryPoolMXBean) iter.next();
            if (pool.getName().equals(name)) {
                if (pool.getType() != type) {
                    throw new RuntimeException("TEST FAILED: " +
                        "Pool " + pool.getName() + " is of type " +
                        pool.getType() + " but expected to be " + type);
                } else {
                    return;
                }
            }
        }
        throw new RuntimeException("TEST FAILED: " +
            "Pool " + name + " is of type " + type +
            " not found");
    }
}