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dunwudunwu
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feat: 更新 java 示例
1 parent d4a6433 commit 85a8835

19 files changed

+557
-123
lines changed

‎codes/javacore-concurrent/src/main/java/io/github/dunwu/javacore/concurrent/CallableDemo.java‎

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This file was deleted.

‎codes/javacore-concurrent/src/main/java/io/github/dunwu/javacore/concurrent/FutureDemo.java‎

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@@ -1,5 +1,6 @@
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package io.github.dunwu.javacore.concurrent;
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import java.util.concurrent.Callable;
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import java.util.concurrent.ExecutionException;
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import java.util.concurrent.ExecutorService;
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import java.util.concurrent.Executors;
@@ -14,7 +15,7 @@ public class FutureDemo {
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public static void main(String[] args) {
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ExecutorService executor = Executors.newCachedThreadPool();
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CallableDemo task = new CallableDemo();
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Task task = new Task();
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Future<Integer> result = executor.submit(task);
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executor.shutdown();
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@@ -35,4 +36,19 @@ public static void main(String[] args) {
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System.out.println("所有任务执行完毕");
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}
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static class Task implements Callable<Integer> {
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@Override
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public Integer call() throws Exception {
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System.out.println("子线程在进行计算");
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Thread.sleep(3000);
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int sum = 0;
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for (int i = 0; i < 100; i++) {
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sum += i;
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}
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return sum;
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}
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}
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}

‎codes/javacore-concurrent/src/main/java/io/github/dunwu/javacore/concurrent/FutureTaskDemo.java‎

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‎codes/javacore-concurrent/src/main/java/io/github/dunwu/javacore/concurrent/error/NotThreadSafeCounter.java‎

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package io.github.dunwu.javacore.concurrent.error;
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import io.github.dunwu.javacore.concurrent.annotation.NotThreadSafe;
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@NotThreadSafe
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public class NotThreadSafeCounter {
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private static long count = 0;
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private void add() {
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int cnt = 0;
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while (cnt++ < 100000) {
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count += 1;
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}
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}
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public static void main(String[] args) throws InterruptedException {
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final NotThreadSafeCounter demo = new NotThreadSafeCounter();
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// 创建两个线程，执行 add() 操作
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Thread t1 = new Thread(() -> {
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demo.add();
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});
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Thread t2 = new Thread(() -> {
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demo.add();
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});
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// 启动两个线程
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t1.start();
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t2.start();
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// 等待两个线程执行结束
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t1.join();
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t2.join();
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System.out.println("count = " + count);
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}
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}
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// 输出：
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// count = 156602
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// 实际结果远小于预期值 200000

‎codes/javacore-concurrent/src/main/java/io/github/dunwu/javacore/concurrent/error/ThreadSafeCounter.java‎

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package io.github.dunwu.javacore.concurrent.error;
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import io.github.dunwu.javacore.concurrent.annotation.ThreadSafe;
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@ThreadSafe
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public class ThreadSafeCounter {
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private static long count = 0;
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private synchronized void add() {
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int cnt = 0;
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while (cnt++ < 100000) {
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count += 1;
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}
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}
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public static void main(String[] args) throws InterruptedException {
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final ThreadSafeCounter demo = new ThreadSafeCounter();
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// 创建两个线程，执行 add() 操作
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Thread t1 = new Thread(() -> {
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demo.add();
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});
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Thread t2 = new Thread(() -> {
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demo.add();
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});
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// 启动两个线程
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t1.start();
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t2.start();
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// 等待两个线程执行结束
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t1.join();
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t2.join();
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System.out.println("count = " + count);
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}
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}
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// 输出：
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// count = 200000

‎codes/javacore-concurrent/src/main/java/io/github/dunwu/javacore/concurrent/jmm/DoubleCheckedLocking.java‎

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package io.github.dunwu.javacore.concurrent.jmm;
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import io.github.dunwu.javacore.concurrent.annotation.NotThreadSafe;
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/**
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* 双重检查锁
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* <p/>
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* Double-checked-locking antipattern
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*
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* @author Brian Goetz and Tim Peierls
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*/
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@NotThreadSafe
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public class DoubleCheckedLocking {
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private static Resource resource;
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public static Resource getInstance() {
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if (resource == null) {
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synchronized (DoubleCheckedLocking.class) {
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if (resource == null) { resource = new Resource(); }
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}
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}
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return resource;
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}
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static class Resource { }
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}

‎codes/javacore-concurrent/src/main/java/io/github/dunwu/javacore/concurrent/jmm/EagerInitialization.java‎

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package io.github.dunwu.javacore.concurrent.jmm;
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import io.github.dunwu.javacore.concurrent.annotation.ThreadSafe;
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/**
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* 饿汉加载初始化（提前加载）
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* <p/>
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* Eager initialization
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*
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* @author Brian Goetz and Tim Peierls
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*/
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@ThreadSafe
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public class EagerInitialization {
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private static Resource resource = new Resource();
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public static Resource getResource() {
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return resource;
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}
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static class Resource { }
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}

‎codes/javacore-concurrent/src/main/java/io/github/dunwu/javacore/concurrent/jmm/PossibleReordering.java‎

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package io.github.dunwu.javacore.concurrent.jmm;
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/**
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* PossibleReordering
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* <p/>
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* Insufficiently synchronized program that can have surprising results
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*
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* @author Brian Goetz and Tim Peierls
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*/
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public class PossibleReordering {
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static int x = 0, y = 0;
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static int a = 0, b = 0;
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public static void main(String[] args) throws InterruptedException {
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Thread one = new Thread(() -> {
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a = 1;
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x = b;
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});
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Thread other = new Thread(() -> {
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b = 1;
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y = a;
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});
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one.start();
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other.start();
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one.join();
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other.join();
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System.out.println("( " + x + ", " + y + " )");
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}
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}
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// 输出：
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// 每次运行结果都不一样，例如：( 0, 1 )、( 1, 0 )、( 1, 1 )

‎codes/javacore-concurrent/src/main/java/io/github/dunwu/javacore/concurrent/jmm/SafeLazyInitialization.java‎

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package io.github.dunwu.javacore.concurrent.jmm;
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import io.github.dunwu.javacore.concurrent.annotation.ThreadSafe;
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/**
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* 懒加载初始化（延迟加载）
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* <p/>
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* Thread-safe lazy initialization
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*
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* @author Brian Goetz and Tim Peierls
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*/
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@ThreadSafe
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public class SafeLazyInitialization {
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private static Resource resource;
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public synchronized static Resource getInstance() {
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if (resource == null) { resource = new Resource(); }
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return resource;
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}
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static class Resource { }
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}

‎codes/javacore-concurrent/src/main/java/io/github/dunwu/javacore/concurrent/jmm/SafeStates.java‎

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package io.github.dunwu.javacore.concurrent.jmm;
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import io.github.dunwu.javacore.concurrent.annotation.ThreadSafe;
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import java.util.HashMap;
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import java.util.Map;
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/**
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* 不可变对象的初始化安全
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* <p/>
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* Initialization safety for immutable objects
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*
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* @author Brian Goetz and Tim Peierls
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*/
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@ThreadSafe
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public class SafeStates {
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private final Map<String, String> states;
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public SafeStates() {
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states = new HashMap<>();
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states.put("alaska", "AK");
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states.put("alabama", "AL");
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// ...
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states.put("wyoming", "WY");
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}
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public String getAbbreviation(String s) {
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return states.get(s);
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}
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}

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