code: public boolean nextBoolean (final double probability)
          {
          if (probability < 0.0 || probability > 1.0)
              throw new IllegalArgumentException ("probability must be between 0.0 and 1.0 inclusive.");
          if (probability==0.0) return false;             // fix half-open issues
          else if (probability==1.0) return true; // fix half-open issues
          return nextDouble() < probability; 
          }
docs: This generates a coin flip with a probability <tt>probability</tt>
  of returning true, else returning false. <tt>probability</tt> must
  be between 0.0 and 1.0, inclusive.
  @param probability
  @return ?