java - 如何打印斐波那契数列，多线程？

Question

任务是编写一个程序，创建并启动两个线程 ThreadFibonacci 和 ThreadOutput。 ThreadFiobnacci 应该计算斐波那契数并将结果放入其静态公共(public)变量中。 ThreadOutput 应输出斐波那契数，并且 ThreadOutput 必须是守护线程。您必须让线程只写出每个斐波那契数一次。我不知道如何完成任务的最后一部分。

只能使用 sleep、interrupt、volatility 和 join。

这是我尝试过的:

import java.util.Scanner;

public class Zadatak2{
  public static void main(String[] args){
    Scanner reader = new Scanner(System.in);
    System.out.println("Enter a number: ");
    int n = reader.nextInt();

    Thread threadFibonaci = new Thread(new ThreadFibonaci(n));
    Thread threadOutput = new ThreadOutput();

    threadFibonaci.start();
    threadOutput.start();

  }
}

class ThreadFibonaci implements Runnable{

  public static volatile long fn;
  private int n;

  public ThreadFibonaci(int n){
    this.n = n;
  }

  public void run(){
    long f0 = 0;
    fn = f0;
    try{
      Thread.sleep(500);
    }catch(Exception e){
      e.printStackTrace();
    }
    long f1 = 1;
    fn = f1;
    try{
      Thread.sleep(500);
    }catch(Exception e){
      e.printStackTrace();
    }
    for(int i=0; i<n; i++){
      fn = f0 + f1;
      f0 = f1;
      f1 = fn;
      try{
        Thread.sleep(500);
      }catch(Exception e){
        e.printStackTrace();
      }
    }
  }
}

class ThreadOutput extends Thread{

  public ThreadOutput(){
    setDaemon(true);
  }

  public void run(){
    while(true){
      System.out.println(ThreadFibonaci.fn);
      try{
        Thread.sleep(500);
      }catch(Exception e){
        e.printStackTrace();
      }
    }
  }
}

Answer 1

您需要再使用一个 volatile 变量来存储当前数字是否已打印的标志

class ThreadFibonaci implements Runnable{

  public static volatile long fn;
  public static volatile boolean printed = false;
  private int n;

  public ThreadFibonaci(int n){
    this.n = n;
  }

  public void run(){
    long f0 = 0;
    fn = f0;
    while (!printed) {
      try{
        Thread.sleep(500);
      }catch(Exception e){
        e.printStackTrace();
      }
    }
    long f1 = 1;
    fn = f1;
    printed = false;
    while (!printed) {
      try{
        Thread.sleep(500);
      }catch(Exception e){
        e.printStackTrace();
      }
    }
    for(int i=0; i<n; i++){
      fn = f0 + f1;
      f0 = f1;
      f1 = fn;
      printed = false;
      while (!printed) {
        try{
          Thread.sleep(500);
        }catch(Exception e){
          e.printStackTrace();
        }
      }
    }
 }
}

class ThreadOutput extends Thread{

 public ThreadOutput(){
   setDaemon(true);
 }

 public void run(){
   while(true){
     while (ThreadFibonaci.printed) {
       try{
         Thread.sleep(500);
        }catch(Exception e){
          e.printStackTrace();
        }
     }
     System.out.println(ThreadFibonaci.fn);
     ThreadFibonaci.printed = true;
  }
 }
}