code: public void intersect( Interval another ) {
          this.lowerBound = Math.max( this.lowerBound, another.lowerBound );
          this.upperBound = Math.min( this.upperBound, another.upperBound );
      }
docs: Calculates the value of the intersection between
  this Interval and another interval.
  This is given by the following rule:
  
  lowerBound = max( this.lowerBound, another.lowerBound )
  upperBound = min( this.upperBound, another.upperBound )
  
  @param another the other interval to calculate the intersection with.