HashMap内存溢出

Author: bootsrc

README.md

@@ -8,6 +8,9 @@ Senior Java engineer interview exams in 2019
 
 ### 面试题来自本人的程序员朋友面试经历，经本人和开源爱好者汇总
 
+* 互联网大厂常考编程题
+  * [Hot!大厂常考编程题，点击进入](readme/pop-exam.md)
+
 * 拍拍贷
   * [使用HashMap的时候如何避免内存泄漏](readme/hashmap-memory-leak.md)
 
@@ -214,8 +217,9 @@ String s = " z111,c888,n222,,,g000, t333,a999,c888 ,p000 ,z111 ";
   * valotile关键字有什么作用
 
   * duboo或者spring cloud微服务调用超时应该怎么处理
-    
-    
+  
+  * sql注入与防止sql注入的方法
+  
 <hr/>
 
 * 京东金融
@@ -269,7 +273,11 @@ String s = " z111,c888,n222,,,g000, t333,a999,c888 ,p000 ,z111 ";
 
   *2.如何自己去实现一个WEB框架，怎么实现类似于SpringMVC里的@RequestMapping,用什么匹配算法速度最快
 
-
+* 蚂蚁金服
+  * 什么是对称加密和非对称加密
+ 
+ 
+ 
 ## 更多Java面试题
 
 部分题目的答案和实例代码在陆续整理中，你们也可以贡献你们的答案。

examset/pom.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>com.lsm</groupId>
+    <artifactId>examset</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+
+</project>

examset/src/main/java/com/lsm/roundrobinprint/RobinPrintReentrantLock.java

@@ -0,0 +1,106 @@
+package com.lsm.roundrobinprint;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
+
+/**
+ * ReentrantLock-Condition实现三个线程交替打印1-75
+ * 结果如下:
+ * <p>
+ * Thread[pool-1-thread-1,5,main]1
+ * Thread[pool-1-thread-2,5,main]2
+ * Thread[pool-1-thread-3,5,main]3
+ * Thread[pool-1-thread-1,5,main]4
+ * Thread[pool-1-thread-2,5,main]5
+ * Thread[pool-1-thread-3,5,main]6
+ * Thread[pool-1-thread-1,5,main]7
+ * Thread[pool-1-thread-2,5,main]8
+ * Thread[pool-1-thread-3,5,main]9
+ * ...
+ * Thread[pool-1-thread-1,5,main]73
+ * Thread[pool-1-thread-2,5,main]74
+ * Thread[pool-1-thread-3,5,main]75
+ * <p>
+ * Condition的含义:
+ * 通过调用condition.await()方法，可以让当前线程在该条件下等待；
+ * 当通过调用condition.signal()方法，又可以唤醒该条件下的等待的线程;
+ */
+public class RobinPrintReentrantLock {
+    private static final int TASK_NUM = 3;
+    private static int num = 0;
+    private static int flag = 0;
+    private static Lock lock = new ReentrantLock();
+    private static List<Condition> list = new ArrayList<Condition>();
+    private static ExecutorService exec = Executors.newCachedThreadPool();
+
+    static {
+        for (int i = 0; i < TASK_NUM; i++) {
+            list.add(lock.newCondition());
+        }
+    }
+
+    private static void crit() {
+        if (num >= 75) {
+            System.exit(1);
+        }
+    }
+
+    private static void print() {
+        crit();
+        System.out.print(Thread.currentThread());
+//        for (int i = 0; i < 5; i++) {
+//            System.out.format("%-2d ", ++num);
+//        }
+
+        System.out.format("%-2d ", ++num);
+        System.out.println();
+    }
+
+    private static void work(int i) {
+        while (!Thread.interrupted()) {
+            lock.lock();
+            try {
+                if (flag == i) {
+                    print();
+                    flag = (i + 1) % list.size();
+                    list.get(flag).signal();
+                } else {
+                    try {
+                        list.get(i % list.size()).await();
+                    } catch (InterruptedException e) {
+                        e.printStackTrace();
+                    }
+                }
+            } finally {
+                lock.unlock();
+            }
+        }
+    }
+
+    private static class Task implements Runnable {
+        private final int i;
+
+        public Task(int i) {
+            this.i = i;
+        }
+
+        @Override
+        public void run() {
+            work(i);
+        }
+
+    }
+
+    /**
+     * @param args
+     */
+    public static void main(String[] args) {
+        for (int i = 0; i < list.size(); i++)
+            exec.execute(new Task(i));
+    }
+}

readme/pop-exam.md

@@ -0,0 +1,21 @@
+# 互联网大厂常考编程题
+
+1.eentrantLock-Condition实现三个线程交替打印1-75
+
+比如结果
+```text
+ * Thread[pool-1-thread-1,5,main]1
+ * Thread[pool-1-thread-2,5,main]2
+ * Thread[pool-1-thread-3,5,main]3
+ * Thread[pool-1-thread-1,5,main]4
+ * Thread[pool-1-thread-2,5,main]5
+ * Thread[pool-1-thread-3,5,main]6
+ * Thread[pool-1-thread-1,5,main]7
+ * Thread[pool-1-thread-2,5,main]8
+ * Thread[pool-1-thread-3,5,main]9
+ * ...
+ * Thread[pool-1-thread-1,5,main]73
+ * Thread[pool-1-thread-2,5,main]74
+ * Thread[pool-1-thread-3,5,main]75
+```
+代码见代码[RobinPrintReentrantLock.java](/examset/src/main/java/com/lsm/roundrobinprint/RobinPrintReentrantLock.java)