code: public boolean nextBoolean (final float probability)
          {
          if (probability < 0.0f || probability > 1.0f)
              throw new IllegalArgumentException ("probability must be between 0.0 and 1.0 inclusive.");
          if (probability==0.0f) return false;            // fix half-open issues
          else if (probability==1.0f) return true;        // fix half-open issues
          return nextFloat() < 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.  Not as precise a random real
  event as nextBoolean(double), but twice as fast. To explicitly
  use this, remember you may need to cast to float first.
  @param probability
  @return ?