有一项任务交给我去做，我已尽力但无法完成。任务是编写一个 Java 程序来生产煎饼，同时随机选择用户来吃生产的煎饼。这两件事必须同时进行，也就是说，在煎饼制作的过程中，用户会检查是否有可用的煎饼制作出来，然后吃掉。每个用户最多可以吃 5 个煎饼，煎饼的生产者预计在给定时间内最多生产 12 个煎饼。整个事情将在 20 秒内发生，然后程序应在 20 秒后终止并打印出报告。指示还指出我应该使这两件事同时运行，但不要使用 Thread 或 ExecutorService。我真的需要一些关于如何实现它的帮助。这是我尝试过的方法，并且在 ProducePancake 方法上出现无限循环，它甚至不允许 eatPancake 方法执行。
public class PanCakeTask {
int consumedPancake = 0;
int availablePancake = 0;
int totalPancakeProduced = 0;
List<String> usersList = new ArrayList<>();
void producePancake(HashMap<String,Integer>users){
// first check the total pancake produced so far by checking the number
// of pancakes eaten by the users plus the available ones
for (String user: users.keySet()){
consumedPancake +=users.get(user);
}
totalPancakeProduced += consumedPancake + availablePancake;
while (totalPancakeProduced <12){
//only continue with the production of pancakes if the number of pancakes
//produced has not been exhausted (i.e 15)
System.out.println("Pancake produced");
//increment the number of pancakes available
availablePancake +=1;
}
}
void eatPancake(HashMap<String,Integer>users){
//first pick the user at random
Collections.shuffle(usersList);
int numberEaten = users.get(usersList.get(0));
//get the user that is on index zero after the list has been shuffled
//then check how many pancake that the picked user has eaten
//because each user is expected to eat a maximum of 5 pancake
if (numberEaten ==5){
//This means that this user has exhausted his/her quota so he/she cannot
//be allowed to eat again
//In this case, the eatPancake method is called again to randomly pick another user
//I am thinking of removing the user from the list here so that he/she cannot be picked again
eatPancake(users);
}else {
//Meaning that the user still has some quota left for him/her to eat
//In this other condition, it will check if there is an available pancake produced
if (availablePancake >=1){
//user will now eat the pancake
//then increment the number of pancake eaten by that user
// and decrement the number of pancakes available
int newCount = numberEaten + 1;
availablePancake -=1;
//finally update the user that just eaten the pancake
users.put(usersList.get(0),newCount);
System.out.println("Eaten a pancake");
}
}
}
public void performTask(){
//Hashmap is used to store the users because of key-value pairs
HashMap <String,Integer> users = new HashMap<>();
users.put("user1",0);
users.put("user2",0);
users.put("user3",0);
usersList.addAll(users.keySet());
System.out.println(users);
System.out.println(usersList);
//This task can only be executed in 20 seconds
long startTimeInSeconds = System.currentTimeMillis()/1000;
long requiredTime = startTimeInSeconds +20;
while (startTimeInSeconds !=requiredTime){
//only continue the process if it has not exceeded 20 seconds
System.out.println("Start time is "+startTimeInSeconds);
System.out.println("End time is "+requiredTime);
//This two method is to be executed concurrently without using Thread or ExecutorService
// I need help on how to achieve that without the use of Thread or ExecutorService
producePancake(users);
eatPancake(users);
startTimeInSeconds = System.currentTimeMillis()/1000;
}
System.out.println("Total number of cake produced is "+totalPancakeProduced);
System.out.println("Total number of cake eaten is "+consumedPancake);
System.out.println("Total number of pancake remained is "+availablePancake);
System.out.println("Time start is "+startTimeInSeconds);
System.out.println("Time completed is "+requiredTime);
}
}
线程并不是真正并行的，除非运行在同一 JVM 中的不同 CPU 上。 不是真正并行意味着线程可能需要在同一个 CPU 上执行几轮，使其看起来像是并行的。
你不能利用Java的线程模型，因此你必须想出类似的东西：