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import java.util.LinkedList;
class GenStack<E> {
private LinkedList<E> list = new LinkedList<E>();
public void push(E item) {
list.addFirst(item);
}
public E pop() {
return list.poll();
}
public E peek() {
return list.peek();
}
public boolean hasItems() {
return !list.isEmpty();
}
public int size() {
return list.size();
}
}
public class GenStackTest {
public static void main(String[] args) {
GenStack<String> gs = new GenStack<String>();
gs.push("One");
gs.push("Two");
gs.push("Three");
gs.push("Four");
System.out.println("There are " + gs.size() + " items in the stack.\n");
System.out.println("The top item is: " + gs.peek() + "\n");
System.out.println("There are still " + gs.size() + " items in the stack.\n");
System.out.println("Popping everything:");
while (gs.hasItems())
System.out.println(gs.pop());
System.out.println("There are now " + gs.size() + " items in the stack.\n");
System.out.println("The top item is: " + gs.peek() + "\n");
}
}
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