PeerStack.java

package checkers.jimmu.examples;

import checkers.jimmu.quals.*;

/**
 * Collection of elements which are owned by the owner of the collection.
 *
 * @author saf
 */
public class PeerStack<T> {

    private static class Cell<CT> {
        private @Peer CT data;
        private @Immutable @Peer Cell next;

        @ReadOnly public @Peer CT getData() {
            return data;
        }

        @ReadOnly public @Immutable @Peer Cell getNext() {
            return next;
        }

        @Anonymous
        public Cell(@Peer CT data, @Immutable @Peer Cell next) {
            this.data = data;
            this.next = next;
        }
    }

    private @Immutable @Peer Cell<T> head;

    public PeerStack() {
        head = null;
    }

    public @Peer T pop() {
        if (head == null) {
            return null;
        } else {
            @Peer T result = head.getData();
            head = head.getNext();
            return result;
        }
    }

    public void push(@Peer T elem) {
        head = new /*@Immutable*/ /*@Peer*/ Cell(elem, head);
    }

    public Boolean isEmpty() {
        return head == null;
    }

}