package week08.basic;
import java.util.Stack;
/**
* 用两个栈来实现一个队列
*
* @author gallenzhang
*
* @param <E>
*/
public class QueueWithTwoStacks<E> {
private Stack<E> stack1;
private Stack<E> stack2;
public QueueWithTwoStacks() {
stack1 = new Stack<E>();
stack2 = new Stack<E>();
}
public boolean isEmpty() {
return stack1.size() == 0;
}
public int size() {
return stack1.size();
}
public void enQueue(E item) {
stack1.push(item);
}
public E deQueue() {
if(stack1.isEmpty()){
return null;
}
while(!stack1.isEmpty()){
stack2.push(stack1.pop());
}
E e = stack2.pop();
while(!stack2.isEmpty()){
stack1.push(stack2.pop());
}
return e;
}
}