我嘗試為消費者創建 2 個線程，為生產者創建 2 個線程。所有 4 個線程都在與一種資源競爭。其中兩個試圖從資源中消費，其中兩個試圖生產。下面是代碼package com.threading;import java.util.ArrayList;import java.util.List;public class TestConsumerProducer2 { protected static int maxSize = 2; static class Consumer implements Runnable { List<Integer> goods; public Consumer(List<Integer> goods) { this.goods = goods; } public void consume() { synchronized (goods) { if (goods.size() <= 0) { try { goods.wait(); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } System.out.println(Thread.currentThread().getName() + " >>>> consuming >>>" + goods.remove(0)); goods.notifyAll(); } } @Override public void run() { for (int i = 0; i < 10; i++) { consume(); try { Thread.currentThread().sleep(100); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } } static class Producer implements Runnable { List<Integer> goods; public Producer(List<Integer> goods) { this.goods = goods; } public void produce(int i) { synchronized (goods) { if (goods.size() >= maxSize) { try { goods.wait(); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } System.out.println(Thread.currentThread().getName() + ">>> producing >> " + i); goods.add(i); goods.notifyAll(); } }
1 回答
千巷貓影
TA貢獻1829條經驗 獲得超7個贊
更改代碼中出現的iftowhile可以解決問題。
Oracle 網站上的Guarded Blocks 教程中有相關建議，其中說：
注意：始終在測試等待條件的循環內調用 wait。不要假設中斷是針對您正在等待的特定條件，或者條件仍然為真。
（中斷是指從等待中返回，不一定是來自調用 Thread.interrupt 的人的實際中斷。）
關鍵點：
只有當線程在檢查時持有鎖時，它才知道貨物列表的內容。
調用 wait 會放棄鎖，允許其他線程在這個線程處于休眠狀態時取得進展。
一旦線程放棄鎖，它之前對貨物列表狀態所做的任何檢查都不再有效。
一旦線程從等待中返回，它就重新獲得了鎖，但該線程需要重新評估條件檢查，否則它正在處理陳舊的信息。在線程上次檢查條件的時間和當前時間之間可能發生了很多事情。您得到 IllegalArgumentException 是因為當前線程假設在當前線程等待時另一個線程刪除了某些東西。
package com.threading;
import java.util.ArrayList;
import java.util.List;
public class TestConsumerProducer2 {
protected static int maxSize = 2;
static class Consumer implements Runnable {
List<Integer> goods;
public Consumer(List<Integer> goods) {
this.goods = goods;
}
public void consume() {
synchronized (goods) {
while (goods.size() <= 0) {
try {
goods.wait();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
System.out.println(Thread.currentThread().getName() + " >>>> consuming >>>" + goods.remove(0));
goods.notifyAll();
}
}
@Override
public void run() {
for (int i = 0; i < 10; i++) {
consume();
try {
Thread.currentThread().sleep(100);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
static class Producer implements Runnable {
List<Integer> goods;
public Producer(List<Integer> goods) {
this.goods = goods;
}
public void produce(int i) {
synchronized (goods) {
while (goods.size() >= maxSize) {
try {
goods.wait();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
System.out.println(Thread.currentThread().getName() + ">>> producing >> " + i);
goods.add(i);
goods.notifyAll();
}
}
@Override
public void run() {
// TODO Auto-generated method stub
for (int i = 0; i < 10; i++) {
produce(i);
try {
Thread.currentThread().sleep(100);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
public static void main(String[] args) {
List<Integer> goods = new ArrayList<>();
Consumer consumer = new Consumer(goods);
Producer producer = new Producer(goods);
Thread consumerWorker1 = new Thread(consumer);
Thread consumerWorker2 = new Thread(consumer);
Thread prroducerWorker1 = new Thread(producer);
Thread prroducerWorker2 = new Thread(producer);
consumerWorker1.start();
consumerWorker2.start();
prroducerWorker1.start();
prroducerWorker2.start();
try {
consumerWorker1.join();
consumerWorker2.join();
prroducerWorker1.join();
prroducerWorker2.join();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("Job completed >>>>");
}
}
代碼現在成功完成，輸出如下：
C:\>java com.threading.TestConsumerProducer2
Thread-2>>> producing >> 0
Thread-1 >>>> consuming >>>0
Thread-3>>> producing >> 0
Thread-0 >>>> consuming >>>0
Thread-2>>> producing >> 1
Thread-3>>> producing >> 1
Thread-0 >>>> consuming >>>1
Thread-1 >>>> consuming >>>1
Thread-2>>> producing >> 2
Thread-3>>> producing >> 2
Thread-0 >>>> consuming >>>2
Thread-1 >>>> consuming >>>2
Thread-2>>> producing >> 3
Thread-0 >>>> consuming >>>3
Thread-3>>> producing >> 3
Thread-1 >>>> consuming >>>3
Thread-2>>> producing >> 4
Thread-0 >>>> consuming >>>4
Thread-3>>> producing >> 4
Thread-1 >>>> consuming >>>4
Thread-2>>> producing >> 5
Thread-0 >>>> consuming >>>5
Thread-3>>> producing >> 5
Thread-1 >>>> consuming >>>5
Thread-2>>> producing >> 6
Thread-0 >>>> consuming >>>6
Thread-3>>> producing >> 6
Thread-1 >>>> consuming >>>6
Thread-2>>> producing >> 7
Thread-0 >>>> consuming >>>7
Thread-3>>> producing >> 7
Thread-1 >>>> consuming >>>7
Thread-2>>> producing >> 8
Thread-0 >>>> consuming >>>8
Thread-3>>> producing >> 8
Thread-1 >>>> consuming >>>8
Thread-2>>> producing >> 9
Thread-0 >>>> consuming >>>9
Thread-3>>> producing >> 9
Thread-1 >>>> consuming >>>9
Job completed >>>>
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