sketch of java/lang/ref/*

classpath/java/lang/ref/ReferenceQueue.java

@@ -0,0 +1,28 @@
+package java.lang.ref;
+
+public abstract class ReferenceQueue<T> {
+  private Reference<? extends T> front;
+  private Reference<? extends T> rear;
+
+  public Reference<? extends T> poll() {
+    Reference<? extends T> r = front;
+    if (front != null) {
+      if (front == front.next) {
+        front = rear = null;
+      } else {
+        front = front.next;
+      }
+    }
+    return r;
+  }
+
+  void add(Reference<? extends T> r) {
+    r.next = r;
+    if (front == null) {
+      front = rear = r;
+    } else {
+      rear.next = r;
+      rear = r;
+    }
+  }
+}