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Multiplier.java

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// file:    Multiplier.java
// author:  Robert M. Keller
// purpose: Example of a Function2 object

/**
 * A Multiplier is a Function2 object that can be used to multiply a
 * pair of Numbers.  If both Numbers are Long or Integer, it returns a
 * Long.  Otherwise it returns a Double.
 */

class Multiplier implements Function2
{
/**
 * Create a Multiplier with a specific scale factor.
 * @param _factor the factor to be used
 */

Multiplier()
  {
  }


/**
 * Apply this Multiplier object to two Objects, both of which should be Numbers.
 * If they are not numbers, a ClassCastException will be thrown.
 *
 * @param x the first argument of this function
 * @param y the second argument of this function
 * @return a Number containing the product of the arguments.  If the arguments
 * are both Integer or Long, it returns a Long.  Otherwise it returns a Double.
 */

public Object apply(Object x, Object y)
  {
  return multiply(x, y);
  }


/**
 * Multiply two Objects, both of which should be Numbers.
 * If they are not numbers, a ClassCastException will be thrown.
 *
 * @param x the first argument of this function
 * @param y the second argument of this function
 * @return a Number containing the product of the arguments.  If the arguments
 * are both Integer or Long, it returns a Long.  Otherwise it returns a Double.
 */

public static Number multiply(Object x, Object y)
  {
  if( (x instanceof Long || x instanceof Integer)
   && (y instanceof Long || y instanceof Integer) )
    {
    long xValue = ((Number)x).longValue();
    long yValue = ((Number)y).longValue();
    return new Long(xValue*yValue);
    }
  else
    {
    double xValue = ((Number)x).doubleValue();
    double yValue = ((Number)y).doubleValue();
    return new Double(xValue*yValue);
    }
  }
}

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