+

vakinge · vakinge · commit 5e466dd82959 · 2018-08-14T12:27:21.000+08:00
diff --git a/README.md b/README.md
@@ -1,7 +1,7 @@
 # Java-interview-coding
 
 #### 初衷
-近几年算起来也面试了不少人(至少三位数)，有初出茅庐的小伙子也有工作10年+的资深架构师，遗憾的是真正对java本身得心应手的少之又少，算的上精通的更是聊胜于无。大部分都是知其然不知所以然（也许那些精通java的都去大厂面试了吧）。于是乎，我按我近年来的java笔记整理了一份面向编码的面试题库，也算是多年心血物尽所用，希望对新鸟老鸟有所帮助。
+整理一份java编码版面试题，一当笔记二分享给有需要的人。
 
 #### 目录
  - 集合
diff --git a/src/io/vakin/algorithm/LRU.java b/src/io/vakin/algorithm/LRU.java
@@ -0,0 +1,125 @@
+package io.vakin.algorithm;
+
+import java.util.HashMap;
+import java.util.Iterator;
+
+public class LRU<K, V> implements Iterable<K> {
+
+    private Node head;
+    private Node tail;
+    private HashMap<K, Node> map;
+    private int maxSize;
+
+    private class Node {
+
+        Node pre;
+        Node next;
+        K k;
+        V v;
+
+        public Node(K k, V v) {
+            this.k = k;
+            this.v = v;
+        }
+    }
+
+    public LRU(int maxSize) {
+
+        this.maxSize = maxSize;
+        this.map = new HashMap<>(maxSize * 4 / 3);
+    }
+
+    public V get(K key) {
+
+        if (!map.containsKey(key)) {
+            return null;
+        }
+
+        Node node = map.get(key);
+        unlink(node);
+        appendHead(node);
+
+        return node.v;
+    }
+
+    public void put(K key, V value) {
+
+    	if(head == null){
+    		head = new Node(key, value);
+    		tail = head;
+    		return;
+    	}
+        if (map.containsKey(key)) {
+            Node node = map.get(key);
+            unlink(node);
+        }
+
+        Node node = new Node(key, value);
+        map.put(key, node);
+        appendHead(node);
+
+        if (map.size() > maxSize) {
+            Node toRemove = removeTail();
+            map.remove(toRemove);
+        }
+    }
+
+    private void unlink(Node node) {
+        Node pre = node.pre;
+        Node next = node.next;
+        if(pre == null){
+        }else {
+        	pre.next = next;
+        	next.pre = pre;
+        }
+    }
+
+    private void appendHead(Node node) {
+        node.next = head;
+        head.pre = node;
+    }
+
+    private Node removeTail() {
+    	Node node = tail;
+    	if(node == null)return null;
+    	tail = tail.pre;
+        return node;
+    }
+
+    @Override
+    public Iterator<K> iterator() {
+
+        return new Iterator<K>() {
+
+            private Node cur = head.next;
+
+            @Override
+            public boolean hasNext() {
+                return cur != tail;
+            }
+
+            @Override
+            public K next() {
+                Node node = cur;
+                cur = cur.next;
+                return node.k;
+            }
+        };
+    }
+    
+    public static void main(String[] args) {
+		LRU<Object, Object> lru = new LRU<>(10);
+		for (int i = 0; i < 5; i++) {
+			lru.put(i, i);
+		}
+		
+		lru.get(3);
+		lru.get(2);
+		
+		Iterator<Object> iterator = lru.iterator();
+		while(iterator.hasNext()){
+			System.out.println(iterator.next());
+		}
+		
+	}
+}
diff --git a/src/io/vakin/concurrent/ConcurrentCounter.java b/src/io/vakin/concurrent/ConcurrentCounter.java
@@ -0,0 +1,15 @@
+package io.vakin.concurrent;
+
+import java.util.concurrent.atomic.AtomicInteger;
+
+/**
+ * 并发下计数器
+ */
+public class ConcurrentCounter {
+
+	AtomicInteger count = new AtomicInteger(0);
+	
+	public int add(){
+		return count.incrementAndGet();
+	}
+}
diff --git a/src/io/vakin/concurrent/CountDownLatchTest.java b/src/io/vakin/concurrent/CountDownLatchTest.java
@@ -0,0 +1,32 @@
+package io.vakin.concurrent;
+
+import java.util.concurrent.CountDownLatch;
+
+
+/**
+ * 
+ * @description <br>
+ * <p>需求:解析一个Excel里多个sheet的数据时，使用多线程每个线程解析一个sheet里的数据，等到所有的sheet都解析完之后，程序需要提示解析完成。</p>
+ * @author <a href="mailto:vakinge@gmail.com">vakin</a>
+ * @date 2018年8月7日
+ */
+public class CountDownLatchTest {
+
+	static CountDownLatch c = new CountDownLatch(2);
+
+	public static void main(String[] args) throws InterruptedException {
+		new Thread(new Runnable() {
+			@Override
+			public void run() {
+				System.out.println("解析中..");
+				c.countDown();
+				System.out.println("解析完成");
+				c.countDown();
+			}
+		}).start();
+
+		//阻塞等到两个子任务完成
+		c.await();
+		System.out.println("全部解析完成");
+	}
+}
