VL-Programmieren/VL13/Aufgabe01/GenericStack.java

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2024-05-07 18:43:58 +00:00
package VL13.Aufgabe01;
/**
* A generic stack.
*/
public class GenericStack<T> {
StackItem<T> start;
/**
* A stack item to store a single item on the stack.
*/
private class StackItem<E> {
E value;
StackItem<E> next;
StackItem<E> prev;
StackItem(E value) {
this.value = value;
}
}
/**
* Method to push a value to the stack.
*
* @param value The value to store on the stack.
*/
public void push(T value) {
if (start == null) {
start = new StackItem<T>(value);
} else {
StackItem<T> item = start;
// get the last item of the stack.
while (item.next != null) {
item = item.next;
}
// create a new stack item to store the value.
item.next = new StackItem<T>(value);
item.next.prev = item;
}
}
/**
* Method to pop a value from the stack.
*
* @return The value from stack.
*/
public T pop() {
StackItem<T> item = start;
// get the last item of the stack.
while (item.next != null) {
item = item.next;
}
// remove last item from stack.
if (item.prev == null) {
start = null;
} else {
item.prev.next = null;
}
// return the value of the last item of the stack.
return item.value;
}
}