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package bjc.esodata;
import java.util.Deque;
import java.util.LinkedList;
/**
* A FIFO implementation of a stack.
*
* Basically, a stack that actually acts like a queue.
*
* @param <T>
* The datatype stored in the stack.
*
* @author Ben Culkin
*/
public class QueueStack<T> extends Stack<T> {
/* Our backing queue. */
private final Deque<T> backing;
/** Create a new empty stack queue. */
public QueueStack() {
backing = new LinkedList<>();
}
@Override
public void push(final T elm) {
backing.add(elm);
}
@Override
public T pop() {
if(backing.isEmpty()) throw new StackUnderflow();
return backing.remove();
}
@Override
public T top() {
if(backing.isEmpty()) throw new StackUnderflow();
return backing.peek();
}
@Override
public int size() {
return backing.size();
}
@Override
public boolean isEmpty() {
return backing.size() == 0;
}
@SuppressWarnings("unchecked")
@Override
public T[] toArray() {
return (T[]) backing.toArray();
}
@Override
public String toString() {
return String.format("QueueStack [backing=%s]", backing);
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + (backing == null ? 0 : backing.hashCode());
return result;
}
@Override
public boolean equals(final Object obj) {
if(this == obj) return true;
if(obj == null) return false;
if(!(obj instanceof QueueStack<?>)) return false;
final QueueStack<?> other = (QueueStack<?>) obj;
if(backing == null) {
if(other.backing != null) return false;
} else if(!backing.equals(other.backing)) return false;
return true;
}
}
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