public static File createVmsJavaOptionFile(String[] cmd) throws IOException 
{
        File script = FILE_UTILS.createTempFile("ANT", ".JAVA_OPTS", null, false, true);
        PrintWriter out = null;
        try {
            out = new PrintWriter(new BufferedWriter(new FileWriter(script)));
            for (int i = 0; i <  cmd.length; i++) {
                out.println(cmd[i]);
            }
        } finally {
            FileUtils.close(out);
        }
        return script;
}

Writes the command into a temporary DCL script and returns the corresponding File object. It is the job of the caller to delete the file on exit.

 public static String getJavaHome() 
{
        return JAVA_HOME;
}

Return the value of ${java.home}

 public static String getJavaVersion() 
{
     
        // Determine the Java version by looking at available classes
        // java.net.Proxy was introduced in JDK 1.5
        // java.lang.CharSequence was introduced in JDK 1.4
        // java.lang.StrictMath was introduced in JDK 1.3
        // java.lang.ThreadLocal was introduced in JDK 1.2
        // java.lang.Void was introduced in JDK 1.1
        // Count up version until a NoClassDefFoundError ends the try
        try {
            javaVersion = JAVA_1_0;
            javaVersionNumber = VERSION_1_0;
            Class.forName("java.lang.Void");
            javaVersion = JAVA_1_1;
            javaVersionNumber++;
            Class.forName("java.lang.ThreadLocal");
            javaVersion = JAVA_1_2;
            javaVersionNumber++;
            Class.forName("java.lang.StrictMath");
            javaVersion = JAVA_1_3;
            javaVersionNumber++;
            Class.forName("java.lang.CharSequence");
            javaVersion = JAVA_1_4;
            javaVersionNumber++;
            Class.forName("java.net.Proxy");
            javaVersion = JAVA_1_5;
            javaVersionNumber++;
            Class.forName("java.util.ServiceLoader");
            javaVersion = JAVA_1_6;
            javaVersionNumber++;
        } catch (Throwable t) {
            // swallow as we've hit the max class version that
            // we have
        }
        kaffeDetected = false;
        try {
            Class.forName("kaffe.util.NotImplemented");
            kaffeDetected = true;
        } catch (Throwable t) {
            // swallow as this simply doesn't seem to be Kaffe
        }
        return javaVersion;
}

Returns the version of Java this class is running under.

 public static int getJavaVersionNumber() 
{
        return javaVersionNumber;
}

Returns the version of Java this class is running under. This number can be used for comparisions; it will always be

 public static String getJdkExecutable(String command) 
{
        if (IS_NETWARE) {
            // Extrapolating from:
            // "NetWare may have a "java" in that directory, but 99% of
            // the time, you don't want to execute it" -- Jeff Tulley
            // < JTULLEY@novell.com >
            return command;
        }
        File jExecutable = null;
        if (IS_AIX) {
            // On IBM's JDK 1.2 the directory layout is different, 1.3 follows
            // Sun's layout.
            jExecutable = findInDir(JAVA_HOME + "/../sh", command);
        }
        if (jExecutable == null) {
            jExecutable = findInDir(JAVA_HOME + "/../bin", command);
        }
        if (jExecutable != null) {
            return jExecutable.getAbsolutePath();
        } else {
            // fall back to JRE bin directory, also catches JDK 1.0 and 1.1
            // where java.home points to the root of the JDK and Mac OS X where
            // the whole directory layout is different from Sun's
            return getJreExecutable(command);
        }
}

Finds an executable that is part of a JDK installation based on the java.home system property.

You typically find them in JAVA_HOME/bin if JAVA_HOME points to your JDK installation.

 public static String getJreExecutable(String command) 
{
        if (IS_NETWARE) {
            // Extrapolating from:
            // "NetWare may have a "java" in that directory, but 99% of
            // the time, you don't want to execute it" -- Jeff Tulley
            // < JTULLEY@novell.com >
            return command;
        }
        File jExecutable = null;
        if (IS_AIX) {
            // On IBM's JDK 1.2 the directory layout is different, 1.3 follows
            // Sun's layout.
            jExecutable = findInDir(JAVA_HOME + "/sh", command);
        }
        if (jExecutable == null) {
            jExecutable = findInDir(JAVA_HOME + "/bin", command);
        }
        if (jExecutable != null) {
            return jExecutable.getAbsolutePath();
        } else {
            // Unfortunately on Windows java.home doesn't always refer
            // to the correct location, so we need to fall back to
            // assuming java is somewhere on the PATH.
            return addExtension(command);
        }
}

Finds an executable that is part of a JRE installation based on the java.home system property.

java, keytool, policytool, orbd, rmid, rmiregistry, servertool and tnameserv are JRE executables on Sun based JRE's.

You typically find them in JAVA_HOME/jre/bin if JAVA_HOME points to your JDK installation. JDK < 1.2 has them in the same directory as the JDK executables.

 public static Vector getJrePackageTestCases() 
{
        Vector tests = new Vector();
        tests.addElement("java.lang.Object");
        switch(javaVersionNumber) {
            case VERSION_1_6:
            case VERSION_1_5:
                tests.addElement(
                    "com.sun.org.apache.xerces.internal.jaxp.datatype.DatatypeFactoryImpl ");
                // Fall tru
            case VERSION_1_4:
                tests.addElement("sun.audio.AudioPlayer");
                if (javaVersionNumber == VERSION_1_4) {
                    tests.addElement("org.apache.crimson.parser.ContentModel");
                    tests.addElement("org.apache.xalan.processor.ProcessorImport");
                    tests.addElement("org.apache.xml.utils.URI");
                    tests.addElement("org.apache.xpath.XPathFactory");
                }
                tests.addElement("org.ietf.jgss.Oid");
                tests.addElement("org.w3c.dom.Attr");
                tests.addElement("org.xml.sax.XMLReader");
                // fall through
            case VERSION_1_3:
                tests.addElement("org.omg.CORBA.Any");
                tests.addElement("com.sun.corba.se.internal.corba.AnyImpl");
                tests.addElement("com.sun.jndi.ldap.LdapURL");
                tests.addElement("com.sun.media.sound.Printer");
                tests.addElement("com.sun.naming.internal.VersionHelper");
                tests.addElement("com.sun.org.omg.CORBA.Initializer");
                tests.addElement("sunw.io.Serializable");
                tests.addElement("sunw.util.EventListener");
                // fall through
            case VERSION_1_2:
                tests.addElement("javax.accessibility.Accessible");
                tests.addElement("sun.misc.BASE64Encoder");
                tests.addElement("com.sun.image.codec.jpeg.JPEGCodec");
                // fall through
            case VERSION_1_1:
            default:
                //things like sun.reflection, sun.misc, sun.net
                tests.addElement("sun.reflect.SerializationConstructorAccessorImpl");
                tests.addElement("sun.net.www.http.HttpClient");
                tests.addElement("sun.audio.AudioPlayer");
                break;
        }
        return tests;
}

Testing helper method; kept here for unification of changes.

 public static Vector getJrePackages() 
{
        if (jrePackages == null) {
            buildJrePackages();
        }
        return jrePackages;
}

get a vector of strings of packages built into that platforms runtime jar(s)

 public static boolean isAtLeastJavaVersion(String version) 
{
        return javaVersion.compareTo(version)  >= 0;
}

Compares the current Java version to the passed in String - assumes the argument is one of the constants defined in this class. Note that Ant now requires JDK 1.2+ so #JAVA_1_0 and #JAVA_1_1 need no longer be tested for.

 public static boolean isJavaVersion(String version) 
{
        return javaVersion.equals(version);
}

Compares the current Java version to the passed in String - assumes the argument is one of the constants defined in this class. Note that Ant now requires JDK 1.2+ so #JAVA_1_0 and #JAVA_1_1 need no longer be tested for.

 public static boolean isKaffe() 
{
        return kaffeDetected;
}

Checks whether the current Java VM is Kaffe.