Tilman
98 lines
1.5 KiB
Java
98 lines
1.5 KiB
Java
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interface Stack {
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public void push(Object o) throws Exception;
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public Object pop();
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public Object peek();
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public boolean isFull();
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}
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class ArrayStack implements Stack {
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Object[] ar;
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int index = 0;
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public ArrayStack(int capacity) {
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ar = new Object[capacity];
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}
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public void push(Object o) throws Exception {
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if (!isFull()) {
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ar[index] = o;
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index++;
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}
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else throw new Exception("Stack is full.");
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}
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public Object pop() {
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if (index > 0) {
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index--;
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return ar[index];
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}
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// alternativ könnte man auch eine Exception werfen
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return null;
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}
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public Object peek() {
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if (index > 0) {
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return ar[index-1];
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}
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// alternativ könnte man auch eine Exception werfen
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return null;
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}
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// pre: index <= ar.length
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public boolean isFull() {
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return (index == ar.length);
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}
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public static void main(String[] args) {
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Stack st = new ArrayStack(3);
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try {
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st.push(new Integer(1));
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st.push(new Integer(2));
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st.push(new Integer(3));
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// der wirft 'ne Exception
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st.push(new Integer(4));
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}
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catch (Exception e) {
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e.printStackTrace();
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}
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System.out.println((Integer) st.pop());
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System.out.println((Integer) st.pop());
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// die 1 kommt doppelt
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System.out.println((Integer) st.peek());
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System.out.println((Integer) st.pop());
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// jetzt ist der Stack leer
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System.out.println((Integer) st.pop());
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}
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}
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