public class Tank extends Object {
/** ~mohammad/public_html/classes/csc241/samples/Tank/Tank.java
   This is a simple tank class. Every Tank object has a capacity of
   5000.0 gallons.  A tank Object is constructed as empty.  We have 
   mutator method(s) that enable us to add water to a tank object
   up to its capcity.  You may also remove any portion of a tank's content.
   We need an accessor method for the current content.  The accesss to
   a tank's content needs to be controlled so that it does not exceed 
   capacity or fall below empty.
**/

  public static final double capacity=5000.0;

  /**Each object of class Tank will have its own variable content_ **/
  protected double content_;

  public Tank() {
  /** Construct a new Tank with 0 content.**/
    content_ = 0.0;
  }

  public double  content () {
  /** Return current content of tank **/
    return content_;
  }

  public void add(double amount) throws
                  TankOverFlowException, IllegalArgumentException {
  /** Add <b>amount</b> to tank's content. If <b>content_</b> 
      would exceeds capacit, method throws <b>TankOverFlowException</b> and 
      the amount is not added. If <b>amount</b> is negative, method 
      throws <b>IllegalArgumentException.</b> **/
     
      if (amount < 0.0) 
        throw new IllegalArgumentException();
      double overflow = (amount+content_) - Tank.capacity;
      if (overflow > 0.0)
        throw new TankOverFlowException(this, overflow);
      content_ +=amount;
  }

  public void remove(double amount) throws
    TankUnderFlowException, IllegalArgumentException {
    /** Remove amount from tank. If removing amount would cause 
        the content to go below <b>capacity</b>, method throws 
        <b>TankUnderFlowException</b> and <b>content_</b> stays the same.
        If <b>amount</b> is negative, this method throws an 
        <b>IllegalArgumentException</b> **/

      if (amount < 0) 
        throw new IllegalArgumentException();
      double underflow = amount - content_;
      if (underflow > 0) 
        throw new TankUnderFlowException(this, underflow);
      content_ -=amount;
    }
  public class TankUnderFlowException extends Exception {
    /** An exception class designed for handling tank content falling
        below empty **/
    public Tank  underflowTank;
    public double underflow;
    public TankUnderFlowException(Tank t, double amount) {
      super(); underflowTank = t; underflow = amount;
    }
  }
  public class TankOverFlowException extends Exception {
    /** An exception class intended for when a tank overflows. **/
    public Tank  overflowTank;
    public double overflow;
    public TankOverFlowException(Tank t, double amount) {
      super(); overflowTank = t; overflow = amount;
    }
  }
}