diff --git a/ListHead.java b/ListHead.java
index 51803e5..3c1bf78 100644
--- a/ListHead.java
+++ b/ListHead.java
@@ -1,33 +1,38 @@
 package  a6;
 
-public class ListHead {
+public final class ListHead {
 
     public ListHead next;
     public ListHead prev;
     public Object data;
 
     public ListHead() {
-        next = this;
-        prev = this;
+        init();
     }
 
-    public void del() {
-
+    public final void del() {
+        next.prev = prev;
+        prev.next = next;
+        init();
     }
 
-    public void delInit() {
-
+    public final void delInit() {
+        del();
     }
 
-    public void addTail(ListHead newNode) {
-
+    public final void addTail(ListHead pnew) {
+        ListHead tmp_prev = prev;
+        prev = pnew;
+        pnew.next = this;
+        pnew.prev = tmp_prev;
+        tmp_prev.next = pnew;
     }
 
-    public Object firstEntry() {
+    public final Object firstEntry() {
         return next.data;
     }
 
-    public void replace(ListHead pnew) {
+    public final void replace(ListHead pnew) {
         pnew.next = next;
         pnew.next.prev = pnew;
         pnew.prev = prev;
@@ -35,17 +40,18 @@ public class ListHead {
         pnew.data = data;
     }
 
-    public void replaceInit(ListHead pnew) {
+    public final void replaceInit(ListHead pnew) {
         replace(pnew);
         init();
     }
 
-    public boolean empty() {
+    public final boolean empty() {
         return next == this;
     }
 
-    public void init() {
-
+    public final void init() {
+        next = this;
+        prev = this;
     }
 
 }
diff --git a/Timer.java b/Timer.java
index 192f114..88727fb 100644
--- a/Timer.java
+++ b/Timer.java
@@ -69,6 +69,7 @@ public class Timer {
     private ListHead[] tv4 = new ListHead[TVN_SIZE];
     private ListHead[] tv5 = new ListHead[TVN_SIZE];
     private ListHead workList = new ListHead();
+    private ListHead cascadeList = new ListHead();
 
     public void init(IGetTickCountFunc func, Object content, int gc_time, int cache_timer_num) {
         this.getTickCount = func;
@@ -86,11 +87,11 @@ public class Timer {
             int index = (int)(timerTick & TVR_MASK);
 
             if (index == 0 &&
-                cascade(tv2, (int)((timerTick >> (TVR_BITS + 0 * TVN_BITS)) & TVN_MASK)) == 0 &&
-                cascade(tv3, (int)((timerTick >> (TVR_BITS + 1 * TVN_BITS)) & TVN_MASK)) == 0 &&
-                cascade(tv4, (int)((timerTick >> (TVR_BITS + 2 * TVN_BITS)) & TVN_MASK)) == 0
+                cascade(tv2, getTimerIndex(index)) == 0 &&
+                cascade(tv3, getTimerIndex(index)) == 0 &&
+                cascade(tv4, getTimerIndex(index)) == 0
                 ) {
-                cascade(tv5, (int)((timerTick >> (TVR_BITS + 3 * TVN_BITS)) & TVN_MASK));
+                cascade(tv5, getTimerIndex(index));
             }
 
             ++timerTick;
@@ -227,7 +228,43 @@ public class Timer {
     }
 
     private int cascade(ListHead[] tv, int index) {
-        return 0;
+        tv[index].replaceInit(cascadeList);
+
+        while (!cascadeList.empty()) {
+            //            internalAddTimer();
+        }
+        cascadeList.init();
+        return index;
+    }
+
+    private final int getTimerIndex(int index) {
+        return (int)((timerTick >> (TVR_BITS + index * TVN_BITS)) & TVN_MASK);
+    }
+
+    private final void internalAddTimer(TimerList timer) {
+        long expires = timer.expires;
+        long idx = expires - timerTick;
+        ListHead vec;
+
+        if (idx < 0) {
+            vec = tv1[(int)(timerTick & TVR_MASK)];
+        } else if (idx < TVR_SIZE) {
+            int i = (int)(expires & TVR_MASK);
+            vec = tv1[i];
+        } else if (idx < (1 << (TVR_BITS + TVN_BITS))) {
+            int i = (int)(expires >> TVR_BITS) & TVN_MASK;
+            vec = tv2[i];
+        } else if (idx < (1 << (TVR_BITS + 2 * TVN_BITS))) {
+            int i = (int)(expires >> (TVR_BITS + TVN_BITS)) & TVN_MASK;
+            vec = tv3[i];
+        } else if (idx < (1 << (TVR_BITS + 3 * TVN_BITS))) {
+            int i = (int)(expires >> (TVR_BITS + 2 * TVN_BITS)) & TVN_MASK;
+            vec = tv4[i];
+        } else {
+            int i = (int)(expires >> (TVR_BITS + 3 * TVN_BITS)) & TVN_MASK;
+            vec = tv5[i];
+        }
+        vec.addTail(vec);
     }
 
 }