public class MultiThreadingRandom { public static void main(String[] args) throws InterruptedException { MultiThreadingRandom multiThreadingRandom = new MultiThreadingRandom(); ExecutorService executorService = Executors.newFixedThreadPool(2); geneRan r1= new geneRan(); geneRan r2= new geneRan(); executorService.submit(r1); executorService.submit(r2); executorService.shutdown(); } } class geneRan implements Runnable{ int rand_int1=0; @Override public void run() { // TODO Implement this method Random rand = new Random(); rand_int1 = rand.nextInt(1000); System.out.println(rand_int1); // System.out.println(ai.getAndIncrement()); } }该程序有时会给出 2 个不同的输出，但有时会给出相同的输出。实际上，我对这两个线程使用了 2 个不同的对象，所以为什么它在某些情况下给出相同的结果。无论如何，我只传递 2 个不同的对象及其线程安全代码。那么我如何才能确保在任何情况下生成 2 个不同的随机数。
2 回答
饮歌长啸
TA贡献1951条经验 获得超3个赞
正如已经评论过的，这与多线程无关。由于数字是随机的，因此它们也有可能相同。
如果你想要 2 个不相同的随机数，你可以这样做：
//Create List of integers
List<Integer> numberPool = new ArrayList<>();
//Initialize list with numbers from 1 to 1000
for(int num = 1; num <= 1000 ; num++) {
numberPool.add(num);
}
//Randomly shuffle list
Collections.shuffle(numberPool);
//Get first number
System.out.println(numberPool.get(0));
//Get second number
System.out.println(numberPool.get(1));
如果你想以多线程方式访问 numberPool，你可以这样做：
public class NumGeneratorThreadSafe{
List<Integer> numberPool = new ArrayList<>();
private int counter = 0;
public NumGeneratorThreadSafe() {
for(int i = 1; i <= 1000 ; i++) {
this.numberPool.add(i);
}
Collections.shuffle(this.numberPool);
}
public synchronized Integer getRandomNumber() {
return this.numberPool.get(this.counter++);
}
public synchronized void resetCounter() {
this.counter = 0;
}
}
希望这可以帮助。
编辑： 为了在线程中使用该类：
public class MultiThreadingRandom {
public static void main(String[] args) throws InterruptedException {
ExecutorService executorService = Executors.newFixedThreadPool(2);
NumGeneratorThreadSafe numGenerator = new NumGeneratorThreadSafe();
GeneRan r1 = new GeneRan(numGenerator);
GeneRan r2 = new GeneRan(numGenerator);
executorService.submit(r1);
executorService.submit(r2);
executorService.shutdown();
}
}
class GeneRan implements Runnable{
private NumGeneratorThreadSafe numGenerator;
public GeneRan(NumGeneratorThreadSafe numGenerator) {
this.numGenerator = numGenerator;
}
@Override
public void run() {
int randInt = this.numGenerator.getRandomNumber();
System.out.println(randInt);
}
}
繁花如伊
TA贡献2012条经验 获得超12个赞
这个怎么样
import java.util.Random;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class MultiThreadingRandom {
public static void main(String[] args) throws InterruptedException, ExecutionException {
ExecutorService executorService = Executors.newFixedThreadPool(2);
Generun r1 = new Generun();
executorService.submit(r1);
Thread.sleep(100);
executorService.submit(r1);
executorService.shutdown();
}
}
class Generun implements Runnable {
int nextInt = -1;
int bound = 1000;
@Override
public void run() {
int temp = nextInt;
nextInt = new Random().nextInt(bound);
if (temp == nextInt) {
do {
nextInt = new Random().nextInt(bound);
} while (temp == nextInt);
}
System.out.println(nextInt);
}
}
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