68 lines
1.3 KiB
Java
68 lines
1.3 KiB
Java
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package VL13.Aufgabe01;
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/**
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* A generic stack.
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*/
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public class GenericStack<T> {
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StackItem<T> start;
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/**
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* A stack item to store a single item on the stack.
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*/
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private class StackItem<E> {
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E value;
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StackItem<E> next;
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StackItem<E> prev;
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StackItem(E value) {
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this.value = value;
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}
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}
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/**
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* Method to push a value to the stack.
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*
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* @param value The value to store on the stack.
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*/
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public void push(T value) {
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if (start == null) {
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start = new StackItem<T>(value);
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} else {
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StackItem<T> item = start;
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// get the last item of the stack.
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while (item.next != null) {
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item = item.next;
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}
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// create a new stack item to store the value.
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item.next = new StackItem<T>(value);
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item.next.prev = item;
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}
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}
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/**
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* Method to pop a value from the stack.
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*
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* @return The value from stack.
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*/
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public T pop() {
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StackItem<T> item = start;
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// get the last item of the stack.
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while (item.next != null) {
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item = item.next;
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}
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// remove last item from stack.
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if (item.prev == null) {
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start = null;
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} else {
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item.prev.next = null;
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}
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// return the value of the last item of the stack.
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return item.value;
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}
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}
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