我们简单的看一下我们自己的代码，我们就知道HashMap被多个线程操作。而Java的文档说HashMap是非线程安全的，应该用ConcurrentHashMap。但是在这里我们可以来研究一下原因。简单代码如下： package com.king.hashmap; import java.util.HashMap; public class TestLock { private HashMap map = new HashMap(); public TestLock() { Thread t1 = new Thread() { public void run() { for (int i = 0; i < 50000; i++) { map.put(new Integer(i), i); } System.out.println("t1 over"); } }; Thread t2 = new Thread() { public void run() { for (int i = 0; i < 50000; i++) { map.put(new Integer(i), i); } System.out.println("t2 over"); } }; Thread t3 = new Thread() { public void run() { for (int i = 0; i < 50000; i++) { map.put(new Integer(i), i); } System.out.println("t3 over"); } }; Thread t4 = new Thread() { public void run() { for (int i = 0; i < 50000; i++) { map.put(new Integer(i), i); } System.out.println("t4 over"); } }; Thread t5 = new Thread() { public void run() { for (int i = 0; i < 50000; i++) { map.put(new Integer(i), i); } System.out.println("t5 over"); } };
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