diff --git a/Chapter3/BinarySearchST.java b/Chapter3/BinarySearchST.java
new file mode 100644
index 0000000..d5ef3e8
--- /dev/null
+++ b/Chapter3/BinarySearchST.java
@@ -0,0 +1,140 @@
+import javax.lang.model.util.ElementScanner6;
+
+/**
+ * BinarySearchST 二分查找的有序符号表
+ */
+public class BinarySearchST<Key extends Comparable<Key>, Value> {
+
+    private Key[] keys;
+    private Value[] vals;
+    private int N;
+
+    public BinarySearchST(int capacity) {
+        keys = (Key[]) new Comparable[capacity];
+        vals = (Value[]) new Object[capacity];
+    }
+
+    public int size() {
+        return N;
+    }
+
+    public boolean isEmpty() {
+        return size() == 0;
+    }
+
+    public Value get(Key key) {
+        if (isEmpty())
+            return null;
+        int i = rank(key);
+        if (i < N && keys[i].compareTo(key) == 0)
+            return vals[i];
+        else
+            return null;
+    }
+
+    public int rank(Key key) {
+        int lo = 0, hi = N - 1;
+        hi = N - 1;
+        while (lo <= hi) {
+            int mid = lo + (hi - lo) / 2;
+            int cmp = key.compareTo(keys[mid]);
+            if (cmp < 0)
+                hi = mid - 1;
+            else if (cmp > 0)
+                lo = mid + 1;
+            else
+                return mid;
+        }
+        return lo;
+    }
+
+    public void put(Key key, Value val) {
+        int i = rank(key);
+        if (i < N && keys[i].compareTo(key) == 0) {
+            vals[i] = val;
+            return;
+        }
+        for (int j = N; j > i; j--) {
+            keys[j] = keys[j - 1];
+            vals[j] = vals[j - 1];
+        }
+        keys[i] = key;
+        vals[i] = val;
+        N++;
+    }
+
+    public void delete(Key key) {
+        int i = rank(key);
+        if (keys[i].compareTo(key) != 0)
+            return;
+        for (int j = i; j < N; j++) {
+            keys[j] = keys[j + 1];
+            vals[j] = vals[j + 1];
+        }
+        N--;
+    }
+
+    public Key min() {
+        return keys[0];
+    }
+
+    public Key max() {
+        return keys[N - 1];
+    }
+
+    public Key select(int k) {
+        return keys[k];
+    }
+
+    public Key ceiling(Key key) {
+        int i = rank(key);
+        return keys[i];
+    }
+
+    public Key floor(Key key) {
+        int i = rank(key);
+        if (keys[i].equals(key))
+            return keys[i];
+        else
+            return keys[i - 1];
+    }
+
+    public Iterable<Key> keys(Key lo, Key hi) {
+        Queue<Key> q = new Queue<Key>();
+        for (int i = rank(lo); i < rank(hi); i++)
+            q.enqueue(keys[i]);
+        if (contains(hi))
+            q.enqueue(keys[rank(hi)]);
+        return q;
+    }
+
+    public boolean contains(Key key) {
+        int lo = 0, hi = N - 1;
+        while (lo <= hi) {
+            int mid = lo + (hi - lo) / 2;
+            int cmp = keys[mid].compareTo(key);
+            if (cmp < 0) {
+                lo = mid + 1;
+            } else if (cmp > 0) {
+                hi = mid - 1;
+            } else
+                return true;
+        }
+        return false;
+    }
+
+    public static void main(String[] args) {
+        BinarySearchST vst = new BinarySearchST<Integer, Integer>(13);
+        for (int i = 0; i < 10; i++) {
+            vst.put(i, i + 10);
+        }
+        if (vst.contains(3))
+            System.out.println("Contains 3");
+        if (!vst.contains(13))
+            System.out.println("13 is not here");
+        vst.delete(3);
+        System.out.println("Deleting 3");
+        if (!vst.contains(3))
+            System.out.println("3 is not here");
+    }
+}
\ No newline at end of file
diff --git a/Chapter3/SequentialSearchST.java b/Chapter3/SequentialSearchST.java
new file mode 100644
index 0000000..a0b8c1f
--- /dev/null
+++ b/Chapter3/SequentialSearchST.java
@@ -0,0 +1,71 @@
+/**
+ * SequentialSearchST
+ */
+public class SequentialSearchST<Key, Value> {
+
+    private Node first;
+
+    private class Node {
+        Key key;
+        Value val;
+        Node next;
+
+        public Node(Key key, Value val, Node next) {
+            this.key = key;
+            this.val = val;
+            this.next = next;
+        }
+    }
+
+    public Value get(Key key) {
+        for (Node x = first; x != null; x = x.next) {
+            if (key.equals(x.key))
+                return x.val;
+        }
+        return null;
+    }
+
+    public void put(Key key, Value val) {
+        for (Node x = first; x != null; x = x.next) {
+            if (key.equals(x.key)) {
+                x.val = val;
+                return;
+            }
+        }
+        first = new Node(key, val, first);
+    }
+
+    public int size() {
+        int size = 0;
+        for (Node x = first; x != null; x = x.next)
+            size++;
+        return size;
+    }
+
+    public void delete(Key key) {
+        for (Node x = first; x != null; x = x.next)
+            if (x.next.key.equals(key)) {
+                x.next = x.next.next;
+                return;
+            }
+    }
+
+    public Iterable<Key> Keys() {
+        Queue<Key> q = new Queue<Key>();
+        for (Node x = first; x != null; x = x.next) {
+            q.enqueue(x.key);
+        }
+        return q;
+    }
+
+    public static void main(String[] args) {
+        SequentialSearchST<Integer, Integer> st = new SequentialSearchST<Integer, Integer>();
+        for (int i = 0; i < 13; i++)
+            st.put(i, i + 10);
+        System.out.printf("value of Key(3) is %d\n", st.get(3));
+        st.delete(3);
+        System.out.println("Deleting key(3)");
+        System.out.printf("The size now is %d\n", st.size());
+
+    }
+}
\ No newline at end of file