package org.jblooming.system;

/**
 * @author Pietro Polsinelli ppolsinelli@open-lab.com
 * @author Roberto Bicchierai rbicchierai@open-lab.com
 */
public class JavaInfo {

  /**
   * Prevent instantiation
   */
  private JavaInfo() {
  }

  /**
   * 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;

  /**
   * 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;

    } catch (ClassNotFoundException e) {
    }
    
    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;
  }

}