finish DList

java/DList/DLink.java

@@ -11,11 +11,46 @@ class DLink<E> {
 
     /** Get and set methods for the data members */
     DLink<E> next() { return next; }
+    
     DLink<E>  setNext(DLink<E> nextval)
     { return next = nextval; }
+    
     DLink<E> prev() { return prev; }
+    
     DLink<E> setPrev(DLink<E> prevval)
     { return prev = prevval; }
+    
     E element() { return element; }
+    
     E setElement(E it) { return element = it; }
+
+    /** Insert "it: at current position */
+    public void insert(E it) {
+	curr.setNext(new DLink<E>(it, curr, curr.next()));
+	curr.next().next().setPrev(curr.next());
+	++cnt;
+    }
+
+    /** Append "it" to the list */
+    public void append(E it) {
+	tail.setPrev(new DLink<E>(it, tail.prev(), tail));
+	tail.prev().prev().setNext(tail.prev());
+	++cnt;
+    }
+
+    /** Remove and return current element */
+    public E remove() {
+	if (curr.next() == tail) return null; // Nothing to remove
+	E it = curr.next().element(); // Remember value
+	curr.next().next().setPrev(curr);
+	curr.setNext(curr.next().next()); // Remove from list
+	--cnt; // Decrement the count
+	return it;
+    }
+
+    /** Move curr one step leftl no change if at front */
+    public void prev() {
+	if (curr != head) // Can't back up from list head
+	    curr = curr.prev();
+    }
 }