azcalv408
asked on
For objects: Followup to IntQueue Class implementation
public int getFront()
{
Integer result = (Integer) data.get(front);
front++;
return result.intValue();
}
I keep getting arrayoutofbound exception, how do I fix this ?
{
Integer result = (Integer) data.get(front);
front++;
return result.intValue();
}
I keep getting arrayoutofbound exception, how do I fix this ?
>>
Integer result = (Integer) data.get(front);
front++;
return result.intValue();
>>
if you're intending there to alter result, you're not doing, btw
Integer result = (Integer) data.get(front);
front++;
return result.intValue();
>>
if you're intending there to alter result, you're not doing, btw
public int getFront()
{
if (front==-1)
{
throw new RuntimeException("Queue is empty");
}
Integer result = (Integer) data.get(front);
front++;
if (front>=data.size())
{
front = -1;
}
return result.intValue();
}
{
if (front==-1)
{
throw new RuntimeException("Queue is empty");
}
Integer result = (Integer) data.get(front);
front++;
if (front>=data.size())
{
front = -1;
}
return result.intValue();
}
Actually not sure I like that
ASKER CERTIFIED SOLUTION
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You seem to be confusing the items that are being queued and the question of indexes/where the front is. From the spec in your previous question, there seems to be no assumptions made about what type of item is being queued, so the following
>>Integer result = (Integer) data.get(front);
doesn't seem to make much sense
>>Integer result = (Integer) data.get(front);
doesn't seem to make much sense
Not sure I follow, and whats that got to do with dealing with an empty queue?
Working from memory (i no longer have the previous code open) the only methods that can affect where front is are the constructor and insert (and the latter sets the position of front). Therefore, the following should be quite adequate
public int getFront()
{
if (data.size() == 0)
{
throw new RuntimeException("Queue is empty");
}
return front;
}
public int getFront()
{
if (data.size() == 0)
{
throw new RuntimeException("Queue is empty");
}
return front;
}
ASKER
>>if (data.size() == 0)
{
throw new RuntimeException("Queue is empty");
}
>> return front;
I think getFront() should return an element of the index front, not the index itself.
{
throw new RuntimeException("Queue is empty");
}
>> return front;
I think getFront() should return an element of the index front, not the index itself.
> I think getFront() should return an element of the index front, not the index itself.
That is correct, and should also increment the index.
The code I posted above should do the trick, let me know if you have any problems with it.
And if so, also post the code you are testing it with.
That is correct, and should also increment the index.
The code I posted above should do the trick, let me know if you have any problems with it.
And if so, also post the code you are testing it with.
Well, i wasn't sure whether you wanted the index or the object. In that case the function should return an Object, not an int (or an Integer).
> should return an Object
That'd be a bit pointless for an IntQueue.
That'd be a bit pointless for an IntQueue.
Well i don't remember seeing what you're meant to be queueing. If it's just numbers and you're not actually removing anything, merely resetting a pointer to the front of the queue, then you may as well just use an int[]. It's a bit pointless using a collection class
ASKER
>>public int getFront()
{
if (front>=data.size())
{
throw new RuntimeException("Queue is empty");
}
Integer result = (Integer) data.get(front);
front++;
return result.intValue();
>>}
objects, your code doesn't seem to work, here's the main test program:
public static void main(String[] args)
{
IntQueue queue1 = new IntQueue();
for(int i = 0; i < 20; i++)
queue1.insert(i);
System.out.println("\n now queue1 = " +queue1);
for(int j = 0; j < 15; j++)
queue1.getFront();
System.out.println("\n now queue1 = " +queue1);
}
the second part of queue1, after the second for loop, queue1 should be [15, 16, 17, 18, 19], but the program gives [0, 1, 2, 3, 4, 5, 6, 7..., 19], same as the first output. Can you see why ?
{
if (front>=data.size())
{
throw new RuntimeException("Queue is empty");
}
Integer result = (Integer) data.get(front);
front++;
return result.intValue();
>>}
objects, your code doesn't seem to work, here's the main test program:
public static void main(String[] args)
{
IntQueue queue1 = new IntQueue();
for(int i = 0; i < 20; i++)
queue1.insert(i);
System.out.println("\n now queue1 = " +queue1);
for(int j = 0; j < 15; j++)
queue1.getFront();
System.out.println("\n now queue1 = " +queue1);
}
the second part of queue1, after the second for loop, queue1 should be [15, 16, 17, 18, 19], but the program gives [0, 1, 2, 3, 4, 5, 6, 7..., 19], same as the first output. Can you see why ?
Think the problems in your toString() method. It should only print elements from front onwards.
ASKER
oh this is all I have for toString
public String toString()
{
String answer = (data).toString();
return answer;
}
how do i print from front to end ?
public String toString()
{
String answer = (data).toString();
return answer;
}
how do i print from front to end ?
SOLUTION
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ASKER
objects, sorry to bug you again but I wrote an equals method and it doesnt seem to work:
public boolean equals(Object obj)
{
if(obj instanceof IntQueue)
{
IntQueue queue = (IntQueue) obj;
return queue.data.subList(front,d ata.size() ).equals
(this.data.subList(front,d ata.size() ));
}
else
return false;
}
can you see what's wrong? thanks a lot
public boolean equals(Object obj)
{
if(obj instanceof IntQueue)
{
IntQueue queue = (IntQueue) obj;
return queue.data.subList(front,d
(this.data.subList(front,d
}
else
return false;
}
can you see what's wrong? thanks a lot
SOLUTION
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:-(
"Though you probably should do a test to ensure you haven't reached end of queue"
so you need:
public int getFront()
{
if( front < 0 || front > data.size() - 1 )
{
System.err.println( "Fell off the end of the data... Wrapping round to the beginning" ) ;
front = 0 ;
}
Integer result = (Integer) data.get(front);
front++;
return result.intValue();
}