Java Tutorial/Development/JDK

Deals with the different version of the Java Virtual Machine.

/*
 * $Id: JVM.java,v 1.3 2009/02/22 02:01:04 kschaefe Exp $
 *
 * Copyright 2004 Sun Microsystems, Inc., 4150 Network Circle,
 * Santa Clara, California 95054, U.S.A. All rights reserved.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * 
 * This library 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
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
import javax.swing.UIManager;
import javax.swing.UIManager.LookAndFeelInfo;
/**
 * Deals with the different version of the Java Virtual Machine. <br>
 */
public class JVM {
  public final static int JDK1_0 = 10;
  public final static int JDK1_1 = 11;
  public final static int JDK1_2 = 12;
  public final static int JDK1_3 = 13;
  public final static int JDK1_4 = 14;
  public final static int JDK1_5 = 15;
  public final static int JDK1_6 = 16;
  public final static int JDK1_6N = 1610;
  public final static int JDK1_7 = 17;
  private static JVM current;
  static {
    current = new JVM();
  }
  /**
   * @return the current JVM object
   */
  public static JVM current() {
    return current;
  }
  private int jdkVersion;
  /**
   * Creates a new JVM data from the <code>java.version</code>
   * System property
   *  
   */
  public JVM() {
    this(System.getProperty("java.version"));
  }
  /**
   * Constructor for the OS object
   */
  public JVM(String p_JavaVersion) {
    if (p_JavaVersion.startsWith("1.7.")) {
      jdkVersion = JDK1_7;
    } else if (p_JavaVersion.startsWith("1.6.")) {
      for (LookAndFeelInfo info : UIManager.getInstalledLookAndFeels()) {
          if ("com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel".equals(info.getClassName())) {
              jdkVersion = JDK1_6N;
              break;
          }
      }
      
      jdkVersion = jdkVersion == 0 ? JDK1_6 : jdkVersion;
    } else if (p_JavaVersion.startsWith("1.5.")) {
      jdkVersion = JDK1_5;
    } else if (p_JavaVersion.startsWith("1.4.")) {
      jdkVersion = JDK1_4;
    } else if (p_JavaVersion.startsWith("1.3.")) {
      jdkVersion = JDK1_3;
    } else if (p_JavaVersion.startsWith("1.2.")) {
      jdkVersion = JDK1_2;
    } else if (p_JavaVersion.startsWith("1.1.")) {
      jdkVersion = JDK1_1;
    } else if (p_JavaVersion.startsWith("1.0.")) {
      jdkVersion = JDK1_0;
    } else {
      // unknown version, assume 1.3
      jdkVersion = JDK1_3;
    }
  }
  public boolean isOrLater(int p_Version) {
    return jdkVersion >= p_Version;
  }
  public boolean isOneDotOne() {
    return jdkVersion == JDK1_1;
  }
  public boolean isOneDotTwo() {
    return jdkVersion == JDK1_2;
  }
  public boolean isOneDotThree() {
    return jdkVersion == JDK1_3;
  }
  public boolean isOneDotFour() {
    return jdkVersion == JDK1_4;
  }
  public boolean isOneDotFive() {
    return jdkVersion == JDK1_5;
  }
  public boolean isOneDotSix() {
    return jdkVersion == JDK1_6;
  }
    /**
     * Determines if the version of JDK1_6 has Nimbus Look and Feel installed.
     * 
     * @return {@code true} if Nimbus is available and the version is 1.6;
     *         {@code false} otherwise
     */
  public boolean isOneDotSixUpdateN() {
      return jdkVersion == JDK1_6N;
  }
  
  public boolean isOneDotSeven() {
      return jdkVersion == JDK1_7;
  }
}

Provides common access to specifics about the version of Java that a virtual machine supports.

/*
 * JBoss, Home of Professional Open Source.
 * Copyright 2006, Red Hat Middleware LLC, and individual contributors
 * as indicated by the @author tags. See the copyright.txt file in the
 * distribution for a full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */

/**
 * Provides common access to specifics about the version of <em>Java</em>
 * that a virtual machine supports.
 *
 * Determines the version of the <em>Java Virtual Machine</em> by checking
 *    for the availablity of version specific classes.
 *
 * Classes are loaded in the following order:
 *    <ol>
 *    <li><tt>java.lang.Void</tt> was introduced in JDK 1.1</li>
 *    <li><tt>java.lang.ThreadLocal</tt> was introduced in JDK 1.2</li>
 *    <li><tt>java.lang.StrictMath</tt> was introduced in JDK 1.3</li>
 *    <li><tt>java.lang.StackTraceElement</tt> was introduced in JDK 1.4</li>
 *    <li><tt>java.lang.Enum</tt> was introduced in JDK 1.5</li>
 *    <li><tt>java.lang.management.LockInfo</tt> was introduced in JDK 1.6</li>
 *    </ol>
 * </p>
 *
 * @version <tt>$Revision: 2240 $</tt>
 * @author  
 */
public final class Java
{
   /** Prevent instantiation */
   private Java() {}
   /** Java version 1.0 token */
   public static final int VERSION_1_0 = 0x01;
   /** Java version 1.1 token */
   public static final int VERSION_1_1 = 0x02;
   /** Java version 1.2 token */
   public static final int VERSION_1_2 = 0x03;
   /** Java version 1.3 token */
   public static final int VERSION_1_3 = 0x04;
   /** Java version 1.4 token */
   public static final int VERSION_1_4 = 0x05;
   
   /** Java version 1.5 token */
   public static final int VERSION_1_5 = 0x06;
   
   /** Java version 1.6 token */
   public static final int VERSION_1_6 = 0x07;
   
   /** 
    * Private to avoid over optimization by the compiler.
    *
    * @see #getVersion()   Use this method to access this final value.
    */
   private static final int VERSION;
   /** Initialize VERSION. */ 
   static
   {
      // default to 1.0
      int version = VERSION_1_0;
      try
      {
         // check for 1.1
         Class.forName("java.lang.Void");
         version = VERSION_1_1;
         // check for 1.2
         Class.forName("java.lang.ThreadLocal");
         version = VERSION_1_2;
         // check for 1.3
         Class.forName("java.lang.StrictMath");
         version = VERSION_1_3;
         // check for 1.4
         Class.forName("java.lang.StackTraceElement");
         version = VERSION_1_4;
         
         // check for 1.5
         Class.forName("java.lang.Enum");
         version = VERSION_1_5;
         
         // check for 1.6
         Class.forName("java.lang.management.LockInfo");
         version = VERSION_1_6;         
      }
      catch (ClassNotFoundException ignore)
      {
      }
      VERSION = version;
   }
   /**
    * Return the version of <em>Java</em> supported by the VM.
    *
    * @return  The version of <em>Java</em> supported by the VM.
    */
   public static int getVersion()
   {
      return VERSION;
   }
   /**
    * Returns true if the given version identifer is equal to the
    * version identifier of the current virtuial machine.
    *
    * @param version    The version identifier to check for.
    * @return           True if the current virtual machine is the same version.
    */
   public static boolean isVersion(final int version)
   {
      return VERSION == version;
   }
   /**
    * Returns true if the current virtual machine is compatible with
    * the given version identifer.
    *
    * @param version    The version identifier to check compatibility of.
    * @return           True if the current virtual machine is compatible.
    */
   public static boolean isCompatible(final int version)
   {
      // if our vm is the same or newer then we are compatible
      return VERSION >= version;
   }
}