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Added Ring Queue(=Circular Queue) #322

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Added Ring Queue(=Circular Queue) #322

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94 changes: 94 additions & 0 deletions Data Structures/Queues/RingQueue.java
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Original file line number Diff line number Diff line change
@@ -0,0 +1,94 @@
public interface Queue {

public void add(Object object);

public Object first();

public Object remove();

public int size();

}
public class RingQueue implements Queue {
private Object[] objArray = null;
private int size;
private int front;
private int rear;

public RingQueue(int n) {
// Create an array of size n
objArray = new Object[n];
size = 0;
front = 0;
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The problem is that for (front+1) % objArray.length the pointer front never reaches the element with index 0 of the array. I would front set equal to -1.

rear = 0;
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The same thing as above.

}

@Override
public void add(Object obj) {
// type obj if there is empty space in the queue
// if there is no empty space in the queue throw new IllegalStateException ("The queue is full");
if (size == objArray.length)
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Please use curly braces. See here for if-else: http://www.oracle.com/technetwork/java/javase/documentation/codeconventions-142311.html#449

throw new IllegalStateException("The queue is full");

else {
rear = (rear + 1) % objArray.length;
objArray[rear] = obj;
size++;
}

}

@Override
public Object first() {
// return the first element if the queue is not empty
// if the queue is empty throw new IllegalStateException ("The queue is empty");
if (size == 0)
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Same thing. Use curly braces

throw new IllegalStateException("The queue is empty");

return objArray[(front + 1) % objArray.length];
}

@Override
public Object remove() {
// If the queue is not empty, delete the first element and return
// if the queue is empty throw new IllegalStateException ("The queue is empty");
Object object = new Object();

if (size == 0)
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Use curly braces, too.

throw new IllegalStateException("The queue is empty");

else {
front = (front + 1) % objArray.length;
object = objArray[front];

size--;
}
return object;
}

@Override
public int size() {
// returns the number of elements stored in the queue
return size;
}

@Override
public String toString() {
StringBuffer sb = new StringBuffer();

if (objArray == null)
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Use curly braces, too.

return sb.toString();

if (front == rear)
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Use curly braces, too.

return sb.toString();

int tempFront = front;
do {
tempFront = (tempFront + 1) % objArray.length;
sb.append(objArray[tempFront]);
} while (tempFront != rear);

return sb.toString();
}

}