src/de/fhswf/in/inf/java1/aufgabe12/BinaryOperator.java


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/**
 * 
 */
package de.fhswf.in.inf.java1.aufgabe12;

import java.util.Stack;

/**
 * An abstract class for calculations with unary operators.
 *
 * @author $Author: $
 * @version $Revision: $, $Date: $ UTC
 */
public abstract class BinaryOperator implements Operator
{
   /*
    * (non-Javadoc)
    * 
    * @see de.fhswf.in.inf.java1.aufgabe12.Operator#eval(java.util.Stack)
    */
   @Override
   public final void eval(Stack<Double> stack)
   {
      if (stack == null)
      {
         throw new IllegalArgumentException("Stack must not be null.");
      }

      if (stack.size() < 2)
      {
         throw new IllegalArgumentException(
               "Unary operation requires one operand.");
      }

      double d2 = stack.pop();
      double d1 = stack.pop();

      stack.push(eval(d1, d2));
   }

   /**
    * This method implements the calculation.
    *
    * @param d1
    *           The first operator.
    * @param d2
    *           The second operator.
    * @return The result of the calculation.
    */
   abstract double eval(double d1, double d2);
}