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/** Test whether the current or a given version is suffiently recent.  A
  * few WWW sites are testing for the browser version and assuming a certain
  * Java version (incorrectly).  This code allows your applet to test whether
  * the host machine's browser or OS is supplying an adequate version of Java
  * to run your code.
  * @author <A HREF="mailto:adahlman@jps.net">Tony Dahlman</A> 
  * @version 1.1 1998/01/01
  */
class VersionTest {

   /** General solution to testing for the java version:  you supply the string
    *  to be tested for compatibility.  This allows various "proprietary" or
    *  deviant properties lists to be handled however you wnat to handle them. 
    *  The 3-parameter morph of isVersionOK() is less general but it handles
    *  version strings like "11" or "1.2beta4".
    *  @param major - required minimum major version.
    *  @param minor - required minimum minor version, if major version is acceptable.
    *  @param bugfix - required minimum minor sub-version, if major & minor versions
    *  are acceptable.
    *  @param testVersion - Here's where you supply a string to be tested, usually but
    *  not always, the result of directly calling String testVersion = 
    *  System.getProperty("java.version").
    */   
   boolean isVersionOK( int major, int minor, int bugfix, String testVersion) {
      int dex = testVersion.indexOf('.');
      if( dex < 1 )  return false;
      try {
         // check major version
         int temp = Integer.parseInt( testVersion.substring(0,dex) );
         if( temp < major ) return false;
         if( temp > major ) return true;
         testVersion = testVersion.substring( dex + 1 );

         // lose any trailing letter as in 1.1.7A
         char ch = testVersion.charAt(testVersion.length()-1);
         if( ! Character.isDigit(ch) )   
            testVersion = testVersion.substring(0,testVersion.length()-1);

         // check minor version
         dex = testVersion.indexOf('.');
         if( dex < 1 ) {     // case of no bugfix number as in 1.2 or 1.0     
            testVersion += ".0";
            dex = testVersion.indexOf('.');
         } 
         temp = Integer.parseInt( testVersion.substring(0,dex) );
         if( temp < minor )  return false;
         if( temp > minor )  return true;

         // check bugfix version
         testVersion = testVersion.substring( dex + 1 );
         temp = Integer.parseInt( testVersion );
         return ( temp >= bugfix );
      } catch ( NumberFormatException e ) {
         System.err.println("Number format exception checking version. Is properties list corrupt?");
         return false;
      } catch ( StringIndexOutOfBoundsException se ) {
         System.err.println("isVersionOK() failed due to input that couldn't be parsed: "+testVersion);
         return false;
      } /* end catch */
   }

   /** A simpler method for testing whether the current java version is
    *  sufficiently recent.   Thanks to Roedy Green <roedy@mindprod.com>
    *  for pointing out some of the pitfalls and making this version test
    *  more robust.
    */
   boolean isVersionOK( int major, int minor, int bugfix) {
      String ver = System.getProperty("java.version");
      if( ver == null )  return false;
      ver = ver.trim();
      if( ver.indexOf('.') < 0 )
         // case of missing dot (Symantec applet viewer)
         ver = ver.charAt(0) + '.' + ver.substring(1);
      int fdex;
      if( ( fdex = find( "beta", ver, true )) > 0 )
         // case of 1.2beta4, and so on...
         ver = ver.substring(0,fdex);

      return isVersionOK( major, minor, bugfix, ver);
   } 

   static int find(String searchString, String testString, boolean caseInsensitive) {
      int len = searchString.length();
      if (caseInsensitive) {
         for (int i=0; i<testString.length()-len + 1; i++) {
            if( testString.regionMatches(true,i,searchString,0,len) )
               return i;
         } /* endfor */
      } else {
         for (int i=0; i<testString.length()-len + 1; i++) {
            if( testString.regionMatches(false,i,searchString,0,len) )
               return i;
         } /* endfor */
      } /* endif */
      return -1;             // return -1 if searchString not found...
   }

   /** Test code to help you evaluate whether isVersionOK() is working well
    *  enough for your program or applet.
    */   
   public static void main(String[] args) throws NumberFormatException {
      VersionTest vt = new VersionTest();
      if( args.length < 3 ) {
         System.out.println("I need 3 command-line parms, such as \"1 0 2\"");
         System.exit(0);
      }
      int major = Integer.parseInt( args[0]);
      int minor = Integer.parseInt( args[1]);
      int bug = Integer.parseInt( args[2]);
      if( args.length == 4 ) {
         String ver = args[3];
         if( (find("beta", ver, true) > 0) ) {
            ver = ver.substring(0, find("beta", ver, true));
            System.out.println("Testing whether the beta version " + ver
                        +" equals or exceeds " + major +"."+ minor +"."+ bug +"...\n"
                        +"isVersionOkay() returns \""
                        + vt.isVersionOK( major, minor, bug, ver ) + "\"\n");
         } else {
            System.out.println("Testing whether version " + ver
                        +" equals or exceeds " + major +"."+ minor +"."+ bug +"...\n"
                        +"isVersionOkay() returns \""
                        + vt.isVersionOK( major, minor, bug, ver ) + "\"\n");
         }
      } else {
         System.out.println("Testing whether the current version "
                        +" equals or exceeds " + major +"."+ minor +"."+ bug +"...\n"
                        +"isVersionOkay() returns \""
                        + vt.isVersionOK( major, minor, bug ) + "\"\n");
      }
   }
}
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