新的起點 新的開始

// 生成一個鎖

Lock lock = new ReentrantLock();

public void accessProtectedResource() {

? lock.lock(); // 取得鎖定

? try {

??? // 對共享資源進行操作

? } finally {

??? // 一定記著把鎖取消掉，鎖本身是不會自動解鎖的

??? lock.unlock();

? }

}

public class FileOperator{

????? // 初始化一個 ReadWriteLock

????? ReadWriteLock lock = new ReentrantReadWriteLock();

public String read() {

????? // 得到 readLock 并鎖定

??????????? Lock readLock = lock.readLock();

?????? ?????readLock.lock();

??????????? try {

????????????????? // 做讀的工作

????????????????? return "Read something";

??????????? } finally {

???????????????? readLock.unlock();

??????????? }

????? }

?????

public void write(String content) {

????? // 得到 writeLock 并鎖定

??????????? Lock writeLock = lock.writeLock();

??????????? writeLock.lock();

??????????? try {

????????????????? // 做讀的工作

??????????? } finally {

???????????????? writeLock.unlock();

??????????? }

????? }

}

public class Basket {?????

Lock lock = new ReentrantLock();

// 產生 Condition 對象

???? Condition produced = lock.newCondition();

???? Condition consumed = lock.newCondition();

???? boolean available = false;

?? ??

???? public void produce() throws InterruptedException {

?????????? lock.lock();

?????????? try {

???????????????? if(available){

??????????????????? consumed.await(); // 放棄 lock 進入睡眠 ?

???????????????? }

???????????????? /* 生產蘋果 */

???????????????? System.out.println("Apple produced.");

???????????????? available = true;

???????????????? produced.signal(); // 發信號喚醒等待這個 Condition 的線程

?????????? } finally {

???????????????? lock.unlock();

?????????? }

???? }

????

???? public void consume() throws InterruptedException {

?????????? lock.lock();

?????????? try {

???????????????? if(!available){

?????????????????????? produced.await();// 放棄 lock 進入睡眠 ?

???????????????? }

???????????????? /* 吃蘋果 */

???????????????? System.out.println("Apple consumed.");

???????????????? available = false;

???????????????? consumed.signal();// 發信號喚醒等待這個 Condition 的線程

?????????? } finally {

???????????????? lock.unlock();

?????????? }

???? }?????

}

public class ConditionTester {

?????

????? public static void main(String[] args) throws InterruptedException{

final Basket basket = new Basket();

// 定義一個 producer

??????????? Runnable producer = new Runnable() {

????????????????? public void run() {

??????????????????????? try {

????????????????????????????? basket.produce();

?????? ?????????????????} catch (InterruptedException ex) {

????????????????????????????? ex.printStackTrace();

??????????????????????? }

????????????????? }

};

// 定義一個 consumer

??????????? Runnable consumer = new Runnable() {

????????????????? public void run() {

??????????????????????? try {

????????????????????????????? basket.consume();

??????????????????????? } catch (InterruptedException ex) {

????????????????????????????? ex.printStackTrace();

??????????????????????? }

????????????????? }

};

// 各產生 10 個 consumer 和 producer

??????????? ExecutorService service = Executors.newCachedThreadPool();

??????????? for(int i=0; i < 10; i++)

????????????????? service.submit(consumer);

??????????? Thread.sleep(2000);

??????????? for(int i=0; i<10; i++)

????????????????? service.submit(producer);

??????????? service.shutdown();

????? }?????

}

public class Pool {

??? ??ArrayList pool = null;

????? Semaphore pass = null;

????? public Pool(int size){

??????????? // 初始化資源池

??????????? pool = new ArrayList();

??????????? for(int i=0; i

????????????????? pool.add("Resource "+i);

??????????? }

??? ????????//Semaphore 的大小和資源池的大小一致

??????????? pass = new Semaphore(size);

????? }

????? public String get() throws InterruptedException{

??????????? // 獲取通行證 , 只有得到通行證后才能得到資源

??????????? pass.acquire();

??????????? return getResource();

????? }

????? public void put(String resource){

??????????? // 歸還通行證，并歸還資源

??????????? pass.release();

??????????? releaseResource(resource);

????? }

???? private synchronized String getResource() {

??????????? String result = pool.get(0);

??????????? pool.remove(0);

??????????? System.out.println("Give out "+result);

??????????? return result;

????? }

????? private synchronized void releaseResource(String resource) {

??????????? System.out.println("return "+resource);

??????????? pool.add(resource);

????? }

}

public class SemaphoreTest {

????? public static void main(String[] args){

??????????? final Pool aPool = new Pool(2);

??????????? Runnable worker = new Runnable() {

????????????????? public void run() {

??????????????????????? String resource = null;

??????? ????????????????try {

????????????????????????????? // 取得 resource

????????????????????????????? resource = aPool.get();

??????????????????????? } catch (InterruptedException ex) {

????????????????????????????? ex.printStackTrace();

??????????????????????? }

??????????????????????? // 用 resource 做工作

??????????????????????? System.out.println("I worked on "+resource);

??????????????????????? // 歸還 resource

??????????????????????? aPool.put(resource);

????????????????? }

??????????? };

??????????? ExecutorService service = Executors.newCachedThreadPool();

??????????? for(int i=0; i<20; i++){

????????????????? service.submit(worker);

??????????? }

??????????? service.shutdown();

????? }????

}