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Fixed unhandled EmptyStackException #2606

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Merged
siriak merged 1 commit into from
Oct 14, 2021
Merged

Fixed unhandled EmptyStackException #2606

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28 changes: 23 additions & 5 deletions Others/QueueUsingTwoStacks.java
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Original file line number Diff line number Diff line change
Expand Up @@ -15,14 +15,14 @@
class QueueWithStack {

// Stack to keep track of elements inserted into the queue
private Stack inStack;
private Stack<Object> inStack;
// Stack to keep track of elements to be removed next in queue
private Stack outStack;
private Stack<Object> outStack;

/** Constructor */
public QueueWithStack() {
this.inStack = new Stack();
this.outStack = new Stack();
this.inStack = new Stack<>();
this.outStack = new Stack<>();
}

/**
Expand Down Expand Up @@ -82,6 +82,24 @@ public Object peekBack() {
public boolean isEmpty() {
return (this.inStack.isEmpty() && this.outStack.isEmpty());
}

/**
* Returns true if the inStack is empty.
*
* @return true if the inStack is empty.
*/
public boolean isInStackEmpty() {
return (inStack.size() == 0);
}

/**
* Returns true if the outStack is empty.
*
* @return true if the outStack is empty.
*/
public boolean isOutStackEmpty() {
return (outStack.size() == 0);
}
}

/**
Expand Down Expand Up @@ -118,7 +136,7 @@ public static void main(String args[]) {
System.out.println(myQueue.isEmpty()); // Will print false

System.out.println(myQueue.remove()); // Will print 1
System.out.println(myQueue.peekBack()); // Will print NULL
System.out.println((myQueue.isInStackEmpty()) ? "null" : myQueue.peekBack()); // Will print NULL
// instack: []
// outStack: [(top) 2, 3, 4]

Expand Down