💡 Documenting source code.

crossoverJie · crossoverJie · commit e4e010ed690b · 2018-04-05T02:45:36.000+08:00
diff --git a/src/main/java/com/crossoverjie/actual/LRUMap.java b/src/main/java/com/crossoverjie/actual/LRUMap.java
@@ -57,6 +57,69 @@ public void put(K key, V value) {
         addNode(key, value);
     }
 
+    public V get(K key){
+
+        Node<K, V> node = getNode(key);
+
+        //移动到头结点
+        moveToHead(node) ;
+
+        return cacheMap.get(key);
+    }
+
+    private void moveToHead(Node<K,V> node){
+
+        //如果是最后的一个节点
+        if (node.tail == null){
+            node.next.tail = null ;
+            tailer = node.next ;
+            nodeCount -- ;
+        }
+
+        //如果是本来就是头节点 不作处理
+        if (node.next == null){
+            return ;
+        }
+
+        //如果处于中间节点
+        if (node.tail != null && node.next != null){
+            //它的上一节点指向它的下一节点 也就删除当前节点
+            node.tail.next = node.next ;
+            nodeCount -- ;
+        }
+
+        //最后在头部增加当前节点
+        //注意这里需要重新 new 一个对象，不然原本的node 还有着下面的引用，会造成内存溢出。
+        node = new Node<>(node.getKey(),node.getValue()) ;
+        addHead(node) ;
+
+    }
+
+    /**
+     * 链表查询 效率较低
+     * @param key
+     * @return
+     */
+    private Node<K,V> getNode(K key){
+        Node<K,V> node = tailer ;
+        while (node != null){
+
+            if (node.getKey().equals(key)){
+                return node ;
+            }
+
+            node = node.next ;
+        }
+
+        return null ;
+    }
+
+
+    /**
+     * 写入头结点
+     * @param key
+     * @param value
+     */
     private void addNode(K key, V value) {
 
         Node<K, V> node = new Node<>(key, value);
@@ -144,6 +207,17 @@ public void setValue(V value) {
 
     @Override
     public String toString() {
-        return cacheMap.toString();
+        StringBuilder sb = new StringBuilder() ;
+        Node<K,V> node = tailer ;
+        while (node != null){
+            sb.append(node.getKey()).append(":")
+                    .append(node.getValue())
+                    .append("-->") ;
+
+            node = node.next ;
+        }
+
+
+        return sb.toString();
     }
 }
diff --git a/src/test/java/com/crossoverjie/actual/LRUMapTest.java b/src/test/java/com/crossoverjie/actual/LRUMapTest.java
@@ -24,4 +24,52 @@ public void put() throws Exception {
         System.out.println(lruMap.toString());
     }
 
+    @Test
+    public void get() throws Exception {
+        LRUMap<String,Integer> lruMap = new LRUMap(3) ;
+        lruMap.put("1",1) ;
+        lruMap.put("2",2) ;
+        lruMap.put("3",3) ;
+
+        System.out.println(lruMap.toString());
+        System.out.println("==============");
+
+        Integer integer = lruMap.get("1");
+        System.out.println(integer);
+        System.out.println("==============");
+        System.out.println(lruMap.toString());
+    }
+
+    @Test
+    public void get3() throws Exception {
+        LRUMap<String,Integer> lruMap = new LRUMap(3) ;
+        lruMap.put("1",1) ;
+        lruMap.put("2",2) ;
+        lruMap.put("3",3) ;
+
+        System.out.println(lruMap.toString());
+        System.out.println("==============");
+
+        Integer integer = lruMap.get("2");
+        System.out.println(integer);
+        System.out.println("==============");
+        System.out.println(lruMap.toString());
+    }
+
+    @Test
+    public void get4() throws Exception {
+        LRUMap<String,Integer> lruMap = new LRUMap(3) ;
+        lruMap.put("1",1) ;
+        lruMap.put("2",2) ;
+        lruMap.put("3",3) ;
+
+        System.out.println(lruMap.toString());
+        System.out.println("==============");
+
+        Integer integer = lruMap.get("3");
+        System.out.println(integer);
+        System.out.println("==============");
+        System.out.println(lruMap.toString());
+    }
+
 }
