java—并发读取文本文件并将数据放入数组的线程

q43xntqr  于 2021-07-09  发布在  Java
关注(0)|答案(3)|浏览(301)

这段代码的目标是运行四个线程,它将打开四个文本文件,从中读取单词,然后将它们放入字符串数组,
我知道的主要问题:
1-我没有将并发函数放在void run函数中,我希望能够将参数传递到该函数中
2-我不确定是否正在修改字符串的全局数组
首先是主要方法:

public static void main(String[] args) throws IOException 
    {
         //declare the threads
         Thread thread1 =  new Thread(ReadFile("list1.txt", Global.array1,"thread1"));
         Thread thread2 =  new Thread(ReadFile("list2.txt", Global.array2,"thread2"));
         Thread thread3 =  new Thread(ReadFile("list3.txt", Global.array3,"thread1"));
         Thread thread4 =  new Thread(ReadFile("list4.txt", Global.array4,"thread2"));

         /*error message from netbeans: cannot find symbol
            symbol:   method ReadFile(java.lang.String,java.lang.String[])

            it says it for every delcaration of the thread*/

         thread1.start();  //putting the threads to work
         thread2.start();
         thread3.start();
         thread4.start();

         thread1.join();   //telling the threads to finish their work
         thread2.join();
         thread3.join();
         thread4.join();

         // merging the arrays into one
         List list = new ArrayList(Arrays.asList(Global.array1));
         list.addAll(Arrays.asList(Global.array2));
         list.addAll(Arrays.asList(Global.array3));
         list.addAll(Arrays.asList(Global.array4));
         Object[] theArray = list.toArray();

           -------------------------etc----------------------------

如果我的声音是对的,这就是“线程类”

public class ReadFile implements Runnable
{
    public void run(){
            //I should get stuff here, that's my problem!!!!
    }

    private String path;
    Thread runner;

    public ReadFile(String filePath, String[] toArray, String threadName) throws IOException
    {
        String path = filePath;
        FileReader fr = new FileReader(path);
        BufferedReader textReader = new BufferedReader(fr);

        int numOfLines = readLines();  
        toArray = new String[numOfLines];

        int i;
        for (i=0; i<numOfLines; i++)
        {
            toArray[i]= textReader.readLine();    //place next line into string array
        }

        textReader.close();
    }

   int readLines() throws IOException
    {
        FileReader fr = new FileReader(filePath);
        BufferedReader bf = new BufferedReader(fr);

        String aLine;
        int noOfLines = 0;

        while((aLine = bf.readLine()) != null)
        {
            noOfLines++;
        }
        bf.close();
        return noOfLines;
    }

    }

最后我为全局变量做了一个类,我不知道这是不是个好主意

public class Global 
{
    public static String[] array1;
    public static String[] array2;
    public static String[] array3;
    public static String[] array4;
}

请让我知道你们的想法,任何帮助或解释或提示将不胜感激

p8ekf7hl

p8ekf7hl1#

您的构造函数签名 ReadFile :

public ReadFile(String filePath, String[] toArray, String threadName)

与中的调用不匹配 main (您只提供 String , String[] ). 我想你的意思是:

Thread thread1 =  new Thread(new ReadFile("list1.txt", Global.array1, "thread1"));
Thread thread2 =  new Thread(new ReadFile("list2.txt", Global.array2, "thread2"));
Thread thread3 =  new Thread(new ReadFile("list3.txt", Global.array3, "thread1"));
Thread thread4 =  new Thread(new ReadFile("list4.txt", Global.array4, "thread2"));

你可能被这个事实搞糊涂了 ReadFile 的构造函数接受 threadName 作为第三个参数,但是 Thread 类本身也有一个类似的参数。

jckbn6z7

jckbn6z72#

三个错误: ReadFile 类是否实现了 Runnable ,因此应该将示例传递给 Thread 施工单位:
thread thread1=新线程(新readfile(“list1.txt”,global.array1),“thread1”);
为什么要创建一个 Thread 内部 ReadFile ? 删除,没有额外的跑步者需要!
这个 ReadFile 构造函数有一个附加参数 threadName 必须移除。

kq4fsx7k

kq4fsx7k3#

如果我们先修复你的文件读取线程,使主要工作发生在 run() 方法:

public class FileReader extends Thread {

  private final File file;
  private String[] lines;

  public FileReader(File file) {
    this.file = file;
  }

  @Override
  public void run() {
    // Read file here (populate `lines`)..
  }

  public String[] getLines() {
    return lines;
  }
}

然后我们可以在 main 方法如下:

public static void main(String[] args) throws Exception {
  List<FileReader> threads = new ArrayList<FileReader>();

  threads.add(new FileReader(new File("foo1")));
  threads.add(new FileReader(new File("foo2")));
  threads.add(new FileReader(new File("foo3")));
  threads.add(new FileReader(new File("foo4")));

  for (FileReader t : threads) {
    t.start();
  }

  List<String> allLines = new ArrayList<String>();

  for (FileReader t : threads) {
    t.join();
    allLines.addAll(Arrays.asList(t.getLines()));
  }    

  // File lines now in allLines
}

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