Java example source code file (Version.java.template)

This example Java source code file (Version.java.template) 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

charsequence, embedded, numberformatexception, string, version

The Version.java.template Java example source code

/*
 * Copyright (c) 1999, 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.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * 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.
 */

package sun.misc;
import java.io.PrintStream;

public class Version {


    private static final String launcher_name =
        "@@launcher_name@@";

    private static final String java_version =
        "@@java_version@@";

    private static final String java_runtime_name =
        "@@java_runtime_name@@";

    private static final String java_profile_name =
        "@@java_profile_name@@";

    private static final String java_runtime_version =
        "@@java_runtime_version@@";

    static {
        init();
    }

    public static void init() {
        System.setProperty("java.version", java_version);
        System.setProperty("java.runtime.version", java_runtime_version);
        System.setProperty("java.runtime.name", java_runtime_name);
    }

    private static boolean versionsInitialized = false;
    private static int jvm_major_version = 0;
    private static int jvm_minor_version = 0;
    private static int jvm_micro_version = 0;
    private static int jvm_update_version = 0;
    private static int jvm_build_number = 0;
    private static String jvm_special_version = null;
    private static int jdk_major_version = 0;
    private static int jdk_minor_version = 0;
    private static int jdk_micro_version = 0;
    private static int jdk_update_version = 0;
    private static int jdk_build_number = 0;
    private static String jdk_special_version = null;

    /**
     * In case you were wondering this method is called by java -version.
     * Sad that it prints to stderr; would be nicer if default printed on
     * stdout.
     */
    public static void print() {
        print(System.err);
    }

    /**
     * This is the same as print except that it adds an extra line-feed
     * at the end, typically used by the -showversion in the launcher
     */
    public static void println() {
        print(System.err);
        System.err.println();
    }

    /**
     * Give a stream, it will print version info on it.
     */
    public static void print(PrintStream ps) {
        boolean isHeadless = false;

        /* Report that we're running headless if the property is true */
        String headless = System.getProperty("java.awt.headless");
        if ( (headless != null) && (headless.equalsIgnoreCase("true")) ) {
            isHeadless = true;
        }

        /* First line: platform version. */
        ps.println(launcher_name + " version \"" + java_version + "\"");

        /* Second line: runtime version (ie, libraries). */

        ps.print(java_runtime_name + " (build " + java_runtime_version);

        if (java_profile_name.length() > 0) {
            // profile name
            ps.print(", profile " + java_profile_name);
        }

        if (java_runtime_name.indexOf("Embedded") != -1 && isHeadless) {
            // embedded builds report headless state
            ps.print(", headless");
        }
        ps.println(')');

        /* Third line: JVM information. */
        String java_vm_name    = System.getProperty("java.vm.name");
        String java_vm_version = System.getProperty("java.vm.version");
        String java_vm_info    = System.getProperty("java.vm.info");
        ps.println(java_vm_name + " (build " + java_vm_version + ", " +
                   java_vm_info + ")");
    }


    /**
     * Returns the major version of the running JVM if it's 1.6 or newer
     * or any RE VM build. It will return 0 if it's an internal 1.5 or
     * 1.4.x build.
     *
     * @since 1.6
     */
    public static synchronized int jvmMajorVersion() {
        if (!versionsInitialized) {
            initVersions();
        }
        return jvm_major_version;
    }

    /**
     * Returns the minor version of the running JVM if it's 1.6 or newer
     * or any RE VM build. It will return 0 if it's an internal 1.5 or
     * 1.4.x build.
     * @since 1.6
     */
    public static synchronized int jvmMinorVersion() {
        if (!versionsInitialized) {
            initVersions();
        }
        return jvm_minor_version;
    }


    /**
     * Returns the micro version of the running JVM if it's 1.6 or newer
     * or any RE VM build. It will return 0 if it's an internal 1.5 or
     * 1.4.x build.
     * @since 1.6
     */
    public static synchronized int jvmMicroVersion() {
        if (!versionsInitialized) {
            initVersions();
        }
        return jvm_micro_version;
    }

    /**
     * Returns the update release version of the running JVM if it's
     * a RE build. It will return 0 if it's an internal build.
     * @since 1.6
     */
    public static synchronized int jvmUpdateVersion() {
        if (!versionsInitialized) {
            initVersions();
        }
        return jvm_update_version;
    }

    public static synchronized String jvmSpecialVersion() {
        if (!versionsInitialized) {
            initVersions();
        }
        if (jvm_special_version == null) {
            jvm_special_version = getJvmSpecialVersion();
        }
        return jvm_special_version;
    }
    public static native String getJvmSpecialVersion();

    /**
     * Returns the build number of the running JVM if it's a RE build
     * It will return 0 if it's an internal build.
     * @since 1.6
     */
    public static synchronized int jvmBuildNumber() {
        if (!versionsInitialized) {
            initVersions();
        }
        return jvm_build_number;
    }

    /**
     * Returns the major version of the running JDK.
     *
     * @since 1.6
     */
    public static synchronized int jdkMajorVersion() {
        if (!versionsInitialized) {
            initVersions();
        }
        return jdk_major_version;
    }

    /**
     * Returns the minor version of the running JDK.
     * @since 1.6
     */
    public static synchronized int jdkMinorVersion() {
        if (!versionsInitialized) {
            initVersions();
        }
        return jdk_minor_version;
    }

    /**
     * Returns the micro version of the running JDK.
     * @since 1.6
     */
    public static synchronized int jdkMicroVersion() {
        if (!versionsInitialized) {
            initVersions();
        }
        return jdk_micro_version;
    }

    /**
     * Returns the update release version of the running JDK if it's
     * a RE build. It will return 0 if it's an internal build.
     * @since 1.6
     */
    public static synchronized int jdkUpdateVersion() {
        if (!versionsInitialized) {
            initVersions();
        }
        return jdk_update_version;
    }

    public static synchronized String jdkSpecialVersion() {
        if (!versionsInitialized) {
            initVersions();
        }
        if (jdk_special_version == null) {
            jdk_special_version = getJdkSpecialVersion();
        }
        return jdk_special_version;
    }
    public static native String getJdkSpecialVersion();

    /**
     * Returns the build number of the running JDK if it's a RE build
     * It will return 0 if it's an internal build.
     * @since 1.6
     */
    public static synchronized int jdkBuildNumber() {
        if (!versionsInitialized) {
            initVersions();
        }
        return jdk_build_number;
    }

    // true if JVM exports the version info including the capabilities
    private static boolean jvmVersionInfoAvailable;
    private static synchronized void initVersions() {
        if (versionsInitialized) {
            return;
        }
        jvmVersionInfoAvailable = getJvmVersionInfo();
        if (!jvmVersionInfoAvailable) {
            // parse java.vm.version for older JVM before the
            // new JVM_GetVersionInfo is added.
            // valid format of the version string is:
            // n.n.n[_uu[c]][-<identifer>]-bxx
            CharSequence cs = System.getProperty("java.vm.version");
            if (cs.length() >= 5 &&
                Character.isDigit(cs.charAt(0)) && cs.charAt(1) == '.' &&
                Character.isDigit(cs.charAt(2)) && cs.charAt(3) == '.' &&
                Character.isDigit(cs.charAt(4))) {
                jvm_major_version = Character.digit(cs.charAt(0), 10);
                jvm_minor_version = Character.digit(cs.charAt(2), 10);
                jvm_micro_version = Character.digit(cs.charAt(4), 10);
                cs = cs.subSequence(5, cs.length());
                if (cs.charAt(0) == '_' && cs.length() >= 3 &&
                    Character.isDigit(cs.charAt(1)) &&
                    Character.isDigit(cs.charAt(2))) {
                    int nextChar = 3;
                    try {
                        String uu = cs.subSequence(1, 3).toString();
                        jvm_update_version = Integer.valueOf(uu).intValue();
                        if (cs.length() >= 4) {
                            char c = cs.charAt(3);
                            if (c >= 'a' && c <= 'z') {
                                jvm_special_version = Character.toString(c);
                                nextChar++;
                            }
                        }
                    } catch (NumberFormatException e) {
                        // not conforming to the naming convention
                        return;
                    }
                    cs = cs.subSequence(nextChar, cs.length());
                }
                if (cs.charAt(0) == '-') {
                    // skip the first character
                    // valid format: <identifier>-bxx or bxx
                    // non-product VM will have -debug|-release appended
                    cs = cs.subSequence(1, cs.length());
                    String[] res = cs.toString().split("-");
                    for (String s : res) {
                        if (s.charAt(0) == 'b' && s.length() == 3 &&
                            Character.isDigit(s.charAt(1)) &&
                            Character.isDigit(s.charAt(2))) {
                            jvm_build_number =
                                Integer.valueOf(s.substring(1, 3)).intValue();
                            break;
                        }
                    }
                }
            }
        }
        getJdkVersionInfo();
        versionsInitialized = true;
    }

    // Gets the JVM version info if available and sets the jvm_*_version fields
    // and its capabilities.
    //
    // Return false if not available which implies an old VM (Tiger or before).
    private static native boolean getJvmVersionInfo();
    private static native void getJdkVersionInfo();
}

// Help Emacs a little because this file doesn't end in .java.
//
// Local Variables: ***
// mode: java ***
// End: ***