Tilman
98 lines
1.7 KiB
Java
98 lines
1.7 KiB
Java
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interface Queue {
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public void enqueue(Object o) throws Exception;
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public Object dequeue();
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public boolean isFull();
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}
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// Implementiert eine Schlange mit einem Array, der
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// eine Art Kreis simuliert
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class ArrayQueue implements Queue {
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Object[] ar;
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int start = 0;
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int elements = 0;
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public ArrayQueue(int capacity) {
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ar = new Object[capacity];
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}
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public void enqueue(Object o) throws Exception {
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if (!isFull()) {
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ar[(start + elements) % ar.length] = o;
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elements++;
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}
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else throw new Exception("Queue is full.");
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}
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public Object dequeue() {
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if (elements > 0) {
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elements--;
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int i = start;
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start = (start+1) % ar.length;
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return ar[i];
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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: elements <= ar.length
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public boolean isFull() {
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return (elements == ar.length);
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}
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public static void main(String[] args) {
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Queue st = new ArrayQueue(3);
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try {
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st.enqueue(new Integer(1));
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st.enqueue(new Integer(2));
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st.enqueue(new Integer(3));
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// der wirft 'ne Exception
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st.enqueue(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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// dann nehmen wir den ersten wieder raus
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System.out.println((Integer) st.dequeue());
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try {
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// jetzt passe die 4 auch noch rein
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st.enqueue(new Integer(4));
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}
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catch (Exception e) {
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// won't happen
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}
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System.out.println((Integer) st.dequeue());
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System.out.println((Integer) st.dequeue());
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System.out.println((Integer) st.dequeue());
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// jetzt ist der Stack leer
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System.out.println((Integer) st.dequeue());
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}
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}
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