length.java

Java程序设计技巧与开发实例附书源代码。

public class Length
{
   private double value = 0;
   private String scale = "none";
   private boolean isValid = false;

   public Length(double _value, String _scale)
   {
      value = _value;
      scale = _scale;
      if ( (value >= 0) && ( (scale.equals("meter"))
                            || (scale.equals("feet"))))
      {
         isValid = true;
      }
   }

   public Length convertTo(String newScale)
   {
      if ( (isValid) && (newScale.equals("feet")))
      {
         return convertToFeet();
      }
      else if ( (isValid) && (newScale.equals("meter")))
      {
         return convertToMeter();
      }
      else
      {
         return new Length( -1.0, "invalid");
      }
   }

   public Length convertToFeet()
   {
      if (scale.equals("feet"))
      {
         return this;
      }
      else
      {
         return new Length(value * 3.2809, "feet");
      }
   }

   public Length convertToMeter()
   {
      if (scale.equals("meter"))
      {
         return this;
      }
      else
      {
         return new Length(value / 3.2809, "meter");
      }
   }

   public void showLength()
   {
      if (isValid)
      {
         System.out.println(value + " " + scale);
      }
      else
      {
         System.out.println("invalid length");
      }
   }

   public double getValue()
   {
      return value;
   }

   public String getScale()
   {
      return scale;
   }

   public boolean isValid()
   {
      return isValid;
   }

   public void setValue(double newValue)
   {
      if (newValue >= 0)
      {
         value = newValue;
      }
      else
      {
         isValid = false;
      }
   }

}