RandomCharStringGen

	/**
	 * Generates a string the length of the argument of Random Characters from
	 * a set of given characters.  Returns the String.
	 * <p>
	 * The string in the method from which characters are chosen can be edited to
	 * add characters and other special symbols.
	 *
	 * @param length -  the number of Random characters to return.
	 * @return
	 */
	static String randChars( int length ){
		int c = length;
		if( c < 0 ) return randChars(Math.abs( c ));
			//err handle or pass
//      return null;
//      throw new IllegalArgumentException();
		else if( length == 0 ) return "";
		else{
			//Add additional chars into the string below if needed.
			final String allChars = "0123456789" // numerals
			                        + "ABCDEFGHIJKLMNOPQRSTUVWXYZ"  //uppercase
			                        + "abcdefghijklmnopqrstuvwxyz";  //lowercase
//              + "!@#$%^&*()"          //Regular Symbols
//               + ",.\\/<>[]{};:'\"`~=-_+ ";  //all other symbols
			
			char[]        chArr = allChars.toCharArray();
			double        x1    = 0.0, x2 = (double)allChars.length();
			StringBuilder sb    = new StringBuilder();
			while( c > 0 ){
				double f = Math.random() / Math.nextDown( 1.0 );
				double x = x1 * ( 1.0 - f ) + x2 * f;
				int    i = (int)Math.floor( x );
				sb.append( chArr[ i ] );
				//or in a single harder to read line:
				//sb.append( allChars.toCharArray()[(int)Math.floor(x1 * ( 1.0 - f ) + x2 * f)]);
				c--;
			}
			return sb.toString();
			}
		}