update hashmap

3 Hash Table/HashMap in Java.md

@@ -2,3 +2,47 @@
 
 java 中 hashmap的实现原理。
 
+```
+public class HashMap<K,V> extends AbstractMap<K,V>
+    implements Map<K,V>, Cloneable, Serializable {
+
+    static class Node<K,V> implements Map.Entry<K,V> {
+        final int hash;
+        final K key;
+        V value;
+        Node<K,V> next;
+        ...
+    }
+
+    static final class TreeNode<K,V> extends LinkedHashMap.Entry<K,V> {
+        TreeNode<K,V> parent;  // red-black tree links
+        TreeNode<K,V> left;
+        TreeNode<K,V> right;
+        TreeNode<K,V> prev;    // needed to unlink next upon deletion
+        boolean red;
+    }
+
+    public V put(K key, V value) {
+        return putVal(hash(key), key, value, false, true);
+    }
+
+    public V get(Object key) {
+        Node<K,V> e;
+        return (e = getNode(hash(key), key)) == null ? null : e.value;
+    }
+
+}
+```
+
+
+### 扩容
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