public class MoveOne
{
// Take a CD from the third slot; put it in the second slot.
public static void main (String[ ] args)
{ Vic sue; // 1
sue = new Vic(); // 2
sue.moveOn(); // 3 move to the second slot
sue.moveOn(); // 4 move to the third slot
sue.takeCD(); // 5 take CD from slot 3, put on stack
sue.backUp(); // 6 move back to the second slot
sue.putCD(); // 7 put CD in slot 2, taken from stack
} //======================
}
public class SmartVic extends Vic
{
public void moveTake()
{ moveOn();
takeCD();
} //======================
public void backPut()
{ backUp();
putCD();
} //======================
}
public class BringThreeBack
{
// Move the CDs in slots 2, 3, and 4 back to slots 1, 2, 3,
// respectively. Presumes a reset with at least 4 slots.
public static void main (String[ ] args)
{ Vic.reset (args); // 1
SmartVic sue; // 2
sue = new SmartVic(); // 3
sue.moveTake(); // 4 move to slot 2 and take CD
sue.backPut(); // 5 back to slot 1 and put CD there
sue.moveOn(); // 6
sue.moveTake(); // 7 move to slot 3 and take CD
sue.backPut(); // 8 back to slot 2 and put CD there
sue.moveOn(); // 9
sue.moveTake(); // 10 move to slot 4 and take CD
sue.backPut(); // 11 back to slot 3 and put CD there
} //======================
}
public class TwoToFour
{
// If a CD is in the second slot, take it out and then
// put it in the fourth slot if possible (robustly).
public static void main (String[ ] args)
{ Vic.reset (args); // 1
Vic sue; // 2
sue = new Vic(); // 3
sue.moveOn(); // 4
if (sue.seesCD()) // 5 if sue sees a CD in slot 2,
{ sue.takeCD(); // 6 then sue takes that CD
sue.moveOn(); // 7
sue.moveOn(); // 8
if (sue.seesSlot()) // 9 if sue has a slot number 4,
sue.putCD(); // 10 then sue puts the CD there
} // 11
} //======================
}
public class ThreeSequences
{
// For each of the first three sequences, move a CD from the
// third slot to the fifth slot, insofar as possible.
public static void main (String[ ] args)
{ Vic.reset (args);
Shifter one;
one = new Shifter(); // design step 1
one.shiftThreeToFive(); // design step 2
Shifter two;
two = new Shifter(); // design step 3
if (two.seesSlot()) // design step 4
{ two.shiftThreeToFive(); // design step 4a
Shifter three;
three = new Shifter(); // design step 4b
if (three.seesSlot()) // design step 4c
three.shiftThreeToFive();
}
} //======================
}
public class Shifter extends Vic
{
// take the CD from slot 3 (if any) and put it in slot 5.
public void shiftThreeToFive()
{ moveOn();
moveOn(); // now in slot 3
if (seesCD())
{ takeCD();
moveOn(); // now in slot 4
if (seesSlot())
{ moveOn(); // now in slot 5
if (seesSlot())
putCD();
}
}
} //======================
}
public class FillThreeApp
{
/** Put a CD in each of the first three slots.
* Stop as soon as you run out of CDs on the stack. */
public static void main (String[ ] args)
{ Vic.say ("This program fills the first three slots.");
Vic.reset (args); // 2
if (Vic.stackHasCD()) // 3
{ Vic sue; // 4
sue = new Vic(); // 5
sue.putCD(); // 6 in slot 1
if (Vic.stackHasCD()) // 7
{ sue.moveOn(); // 8 to slot 2
sue.putCD(); // 9
if (Vic.stackHasCD()) // 10
{ sue.moveOn(); // 11 to slot 3
sue.putCD(); // 12
} // 13
} // 14
} // 15
Vic.say ("All done!"); // 16
} //======================
}
public class TwoVics
{
/** Take the CD in slot 1 if there is one, otherwise put a
* CD there; repeat for the second sequence, if any. */
public static void main (String[ ] args)
{ Vic first; // 1
first = new Vic(); // 2
if (first.seesCD()) // 3
first.takeCD(); // 4
else // 5
first.putCD(); // 6
Vic second; // 7
second = new Vic(); // 8
if (second.seesSlot()) // 9
{ if (second.seesCD()) // 10
second.takeCD(); // 11
else // 12
second.putCD(); // 13
} // 14
} //======================
}
public class Checker extends Vic
{
/** Tell whether the stack has at least two CDs.
* Precondition: the executor is not at the end
* of its slots and the current slot is empty. */
public boolean hasTwoOnStack()
{ if ( ! stackHasCD()) // 1
return false; // 2
putCD(); // 3
if (stackHasCD()) // 4
{ takeCD(); // 5
return true; // 6
} // 7
else // 8
{ takeCD(); // 9
return false; // 10
} // 11
} //======================
/** Tell whether the executor's current slot and the one
* after it exist and have no CD. No precondition. */
public boolean seesTwoEmpty()
{ if ( ! seesSlot()) // 12
return false; // 13
if (seesCD()) // 14
return false; // 15
moveOn(); // 16
if (seesSlot()) // 17
{ if ( ! seesCD()) // 18
{ backUp(); // 19
return true; // 20
} // 21
} // 22
backUp(); // 23
return false; // 24
} //======================
}
public class CheckerRewritten extends Vic // improved version
{
/** Tell whether the stack has at least two CDs.
* Precondition: the executor is not at the end
* of its slots and the current slot is empty. */
public boolean hasTwoOnStack()
{ if ( ! stackHasCD()) // 1
return false; // 2
putCD(); // 3 modify state
boolean result; // 4
result = stackHasCD(); // 5
takeCD(); // 6 restore state
return result; // 7
} //======================
/** Tell whether the executor's current slot and the
* one after it exist and have no CD. No precondition. */
public boolean seesTwoEmpty()
{ if ( ! seesSlot() || seesCD())
return false;
moveOn();
boolean valueToReturn;
valueToReturn = seesSlot() && ! seesCD();
backUp();
return valueToReturn;
} //======================
}
|
2