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Fix unhandled EmptyStackException (#2606)

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Aitor Fidalgo Sánchez 2021-10-14 12:25:38 +02:00 committed by GitHub
parent b83bb0178d
commit 8094798c46
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1 changed files with 23 additions and 5 deletions
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28
Others/QueueUsingTwoStacks.java
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@ -15,14 +15,14 @@ import java.util.Stack;
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<>();
}
/**
@ -82,6 +82,24 @@ class QueueWithStack {
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);
}
}
/**
@ -118,7 +136,7 @@ public class QueueUsingTwoStacks {
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]