问java.lang.RuntimeException:不可编译的源代码

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// A fixed-size queue class for characters that uses exceptions.
class FixedQueue implements ICharQ {
    private char q[]; // this array holds the queue
    private int putloc, getloc; // the put and get indices

    // Construct an empty queue given its size.
    public FixedQueue(int size) {
        q = new char[size]; // allocate memory for queue
        putloc = getloc = 0;
    }

    // Put a character into the queue.
    public void put(char ch) throws QueueFullException {

        if(putloc==q.length)
            throw new QueueFullException(q.length);

        q[putloc++] = ch;
    }

    // Get a character from the queue.
    public char get() throws QueueEmptyException {

        if(getloc == putloc)
            throw new QueueEmptyException();

        return q[getloc++];
    }
}

// A character queue interface.
public interface ICharQ {
    // Put a character into the queue.
    void put (char ch) throws QueueFullException;

    // Get a character from the queue.
    char get() throws QueueEmptyException;
}

// Demonstrate the queue exceptions.
class QExcDemo {
    public static void main(String args[]) {
        FixedQueue q = new FixedQueue(10);
        char ch;
        int i;

        try {
            // over-empty the queue
            for(i=0; i<11; i++) {
                System.out.print("Getting next char: ");
                ch = q.get();
                System.out.println(ch);
            }
        }
        catch(QueueEmptyException exc) {
            System.out.println(exc);
        }
    }
}

// An exception for queue-empty errors.
public class QueueEmptyException extends Exception {

    public String toString() {
        return "\nQueue is empty.";
    }
}

// An exception for queue-full errors.
public class QueueFullException extends Exception {
    int size;

    QueueFullException(int s) { size = s; }

    public String toString() {
        return "\nQueue is full. Maximum size is " + size;
    }
}