Here you can find the source of getThreadDumpId()
private static int getThreadDumpId()
//package com.java2s; /*/*from w w w. j a v a 2 s . c o m*/ * Copyright (c) 2016, 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.util.concurrent.atomic.AtomicInteger; public class Main { /** * This generates a per thread persistent id to aid mapping related dump files with each other. */ private static final ThreadLocal<Integer> threadDumpId = new ThreadLocal<>(); private static final AtomicInteger dumpId = new AtomicInteger(); private static int getThreadDumpId() { Integer id = threadDumpId.get(); if (id == null) { id = dumpId.incrementAndGet(); threadDumpId.set(id); } return id; } }