systemutils.java

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/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2002-2003 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowledgement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgement may appear in the software itself,
 *    if and wherever such third-party acknowledgements normally appear.
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 *    Foundation" must not be used to endorse or promote products derived
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 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
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package org.apache.commons.lang;

/**
 * <p>Helpers for <code>java.lang.System</code>.</p>
 * 
 * <p>If a system property cannot be read due to security restrictions, 
 * the corresponding field in this class will be set to <code>null</code>
 * and a message will be written to <code>System.err</code>.</p>
 *
 * @author Based on code from Avalon Excalibur
 * @author Based on code from Lucene
 * @author Stephen Colebourne
 * @author <a href="mailto:[e-mail]">Steve Downey</a>
 * @author Gary Gregory
 * @author Michael Becke
 * @author Tetsuya Kaneuchi
 * @since 1.0
 * @version $Id: SystemUtils.java,v 1.23 2003/08/22 16:34:06 ggregory Exp $
 */
public class SystemUtils {

    // System property constants
    //-----------------------------------------------------------------------
    // These MUST be declared first. Other constants depend on this.
    
    /**
     * <p>The <code>file.encoding</code> System Property.</p>
     * <p>File encoding, such as <code>Cp1252</code>.</p>
     * 
     * <p>Defaults to <code>null</code> if the runtime does not have
     * security access to read this property or the property does not exist.</p>
     * 
     * @since 2.0
     * @since Java 1.2.
     */
    public static final String FILE_ENCODING = getSystemProperty("file.encoding");

    /**
     * <p>The <code>file.separator</code> System Property.
     * File separator (<code>&quot;/&quot;</code> on UNIX).</p>
     *
     * <p>Defaults to <code>null</code> if the runtime does not have
     * security access to read this property or the property does not exist.</p>
     * 
     * @since Java 1.1.
     */
    public static final String FILE_SEPARATOR = getSystemProperty("file.separator");

    /**
     * <p>The <code>java.class.path</code> System Property. Java class path.</p>
     *
     * <p>Defaults to <code>null</code> if the runtime does not have
     * security access to read this property or the property does not exist.</p>
     * 
     * @since Java 1.1.
     */
    public static final String JAVA_CLASS_PATH = getSystemProperty("java.class.path");

    /**
     * <p>The <code>java.class.version</code> System Property.
     * Java class format version number.</p>
     *
     * <p>Defaults to <code>null</code> if the runtime does not have
     * security access to read this property or the property does not exist.</p>
     * 
     * @since Java 1.1.
     */
    public static final String JAVA_CLASS_VERSION = getSystemProperty("java.class.version");

    /**
     * <p>The <code>java.compiler</code> System Property. Name of JIT compiler to use.
     * First in JDK version 1.2. Not used in Sun JDKs after 1.2.</p>
     *
     * <p>Defaults to <code>null</code> if the runtime does not have
     * security access to read this property or the property does not exist.</p>
     * 
     * @since Java 1.2. Not used in Sun versions after 1.2.
     */
    public static final String JAVA_COMPILER = getSystemProperty("java.compiler");

    /**
     * <p>The <code>java.ext.dirs</code> System Property. Path of extension directory
     * or directories.</p>
     *
     * <p>Defaults to <code>null</code> if the runtime does not have
     * security access to read this property or the property does not exist.</p>
     * 
     * @since Java 1.3
     */
    public static final String JAVA_EXT_DIRS = getSystemProperty("java.ext.dirs");

    /**
     * <p>The <code>java.home</code> System Property. Java installation directory.</p>
     *
     * <p>Defaults to <code>null</code> if the runtime does not have
     * security access to read this property or the property does not exist.</p>
     * 
     * @since Java 1.1
     */
    public static final String JAVA_HOME = getSystemProperty("java.home");

    /**
     * <p>The <code>java.io.tmpdir</code> System Property. Default temp file path.</p>
     *
     * <p>Defaults to <code>null</code> if the runtime does not have
     * security access to read this property or the property does not exist.</p>
     * 
     * @since Java 1.2
     */
    public static final String JAVA_IO_TMPDIR = getSystemProperty("java.io.tmpdir");

    /**
     * <p>The <code>java.library.path</code> System Property. List of paths to search
     * when loading libraries.</p>
     *
     * <p>Defaults to <code>null</code> if the runtime does not have
     * security access to read this property or the property does not exist.</p>
     * 
     * @since Java 1.2
     */
    public static final String JAVA_LIBRARY_PATH = getSystemProperty("java.library.path");

    /**
     * <p>The <code>java.runtime.name</code> System Property. Java Runtime Environment
     * name.</p>
     *
     * <p>Defaults to <code>null</code> if the runtime does not have
     * security access to read this property or the property does not exist.</p>
     * 
     * @since 2.0
     * @since Java 1.3
     */
    public static final String JAVA_RUNTIME_NAME = getSystemProperty("java.runtime.name");

    /**
     * <p>The <code>java.runtime.version</code> System Property. Java Runtime Environment
     * version.</p>
     *
     * <p>Defaults to <code>null</code> if the runtime does not have
     * security access to read this property or the property does not exist.</p>
     * 
     * @since 2.0
     * @since Java 1.3
     */
    public static final String JAVA_RUNTIME_VERSION = getSystemProperty("java.runtime.version");

    /**
     * <p>The <code>java.specification.name</code> System Property. Java Runtime Environment
     * specification name.</p>
     *
     * <p>Defaults to <code>null</code> if the runtime does not have
     * security access to read this property or the property does not exist.</p>
     * 
     * @since Java 1.2
     */
    public static final String JAVA_SPECIFICATION_NAME = getSystemProperty("java.specification.name");

    /**
     * <p>The <code>java.specification.vendor</code> System Property. Java Runtime Environment
     * specification vendor.</p>
     *
     * <p>Defaults to <code>null</code> if the runtime does not have
     * security access to read this property or the property does not exist.</p>
     * 
     * @since Java 1.2
     */
    public static final String JAVA_SPECIFICATION_VENDOR = getSystemProperty("java.specification.vendor");

    /**
     * <p>The <code>java.specification.version</code> System Property. Java Runtime Environment
     * specification version.</p>
     *
     * <p>Defaults to <code>null</code> if the runtime does not have
     * security access to read this property or the property does not exist.</p>
     * 
     * @since Java 1.3
     */
    public static final String JAVA_SPECIFICATION_VERSION = getSystemProperty("java.specification.version");

    /**
     * <p>The <code>java.vendor</code> System Property. Java vendor-specific string.</p>
     *
     * <p>Defaults to <code>null</code> if the runtime does not have
     * security access to read this property or the property does not exist.</p>
     * 
     * @since Java 1.1
     */
    public static final String JAVA_VENDOR = getSystemProperty("java.vendor");

    /**
     * <p>The <code>java.vendor.url</code> System Property. Java vendor URL.</p>
     *
     * <p>Defaults to <code>null</code> if the runtime does not have
     * security access to read this property or the property does not exist.</p>
      * 
     * @since Java 1.1
    */
    public static final String JAVA_VENDOR_URL = getSystemProperty("java.vendor.url");

    /**
     * <p>The <code>java.version</code> System Property. Java version number.</p>
     *
     * <p>Defaults to <code>null</code> if the runtime does not have
     * security access to read this property or the property does not exist.</p>
     * 
     * @since Java 1.1
     */
    public static final String JAVA_VERSION = getSystemProperty("java.version");

    /**
     * <p>The <code>java.vm.info</code> System Property. Java Virtual Machine implementation
     * info.</p>
     *
     * <p>Defaults to <code>null</code> if the runtime does not have
     * security access to read this property or the property does not exist.</p>
     * 
     * @since 2.0
     * @since Java 1.2
     */
    public static final String JAVA_VM_INFO = getSystemProperty("java.vm.info");

    /**
     * <p>The <code>java.vm.name</code> System Property. Java Virtual Machine implementation
     * name.</p>
     *
     * <p>Defaults to <code>null</code> if the runtime does not have
     * security access to read this property or the property does not exist.</p>
     * 
     * @since Java 1.2
     */
    public static final String JAVA_VM_NAME = getSystemProperty("java.vm.name");

    /**
     * <p>The <code>java.vm.specification.name</code> System Property. Java Virtual Machine
     * specification name.</p>
     *
     * <p>Defaults to <code>null</code> if the runtime does not have
     * security access to read this property or the property does not exist.</p>
     * 
     * @since Java 1.2
     */
    public static final String JAVA_VM_SPECIFICATION_NAME = getSystemProperty("java.vm.specification.name");