java数组实现队列

Posted 2021-02-05 pu20065226

package Algorithm;

/**
 * @author [email protected]</br> Created By: 2019-1-22 下午2:41:32
 */
public class QueueByArray {
    private Object[] queue;
    final static int DEFAULT_MAX_SIZE = 100;
    int length, head, tail;

    private void init() {
        queue = new Object[length];
        head = tail = 0;
    }

    QueueByArray() {
        length = DEFAULT_MAX_SIZE;
        init();
    }

    QueueByArray(int size) {
        length = size;
        init();
    }

    public boolean isFull() {
        if (queue[tail] != null) {// exclude the inition status
            return tail % length == head;// tail++ when put
        }

        return false;

    }

    public boolean isEmpty() {
        if (queue[tail] != null) {// exclue the full status
            return false;
        }
        return tail == head;// head ++ when got
    }

    public int size() {
        if (isFull()) {
            return length;
        }
        if (isEmpty()) {
            return 0;
        }

        return (tail - head + length) % length;
    }

    public void clear() {
        queue = null;
        queue = new Object[length];
    }

    // in queue
    public void put(Object o) throws Exception {
        if (isFull()) {
            System.out.println(head);
            System.out.println(tail);
            throw new Exception("the queue is full!");
        } else {
            queue[tail] = o;
            tail = (tail + 1) % length;
        }
    }

    // out queue
    public Object get() throws Exception {
        if (isEmpty()) {
            throw new Exception("the queue is empty!");
        } else {
            final Object o = queue[head];
            queue[head] = null;
            head = (head + 1) % length;
            return o;
        }
    }

    public static void main(String[] args) throws Exception {
        final QueueByArray myqueue = new QueueByArray(3);

        for (int i = 111; i < 114; i++) {
            myqueue.put(i);
        }
        System.out.println("head==" + myqueue.head + ";tail==" + myqueue.tail + ";size=="
                + myqueue.size());

        while (myqueue.size() > 0) {
            System.out.println(myqueue.get());
        }

    }

}

输出：

head==0;tail==0;size==3
111
112
113