小编mar*_*rek的帖子

我有一些方法将一些数据写入文件.我使用PrintWriter,BufferedWriter并且FileWriter如下所示

public void writeToFile(String FileName){
    PrintWriter pw = null;
    try {
        pw = new PrintWriter(new BufferedWriter(new FileWriter(FileName)));
        for(Cars car : list){
            pw.println(car.getType());
            pw.println(car.getMaxSpeed());
            pw.println(car.getOwner());
            pw.println();
            pw.flush();
        }
        pw.close();
    }
    catch(IOException ex){
        System.err.println(ex);
    }
}

现在我如何从文件中读取这些数据？我试图用InputStreamReader,BufferedReader和FileInputStream,但我的NetBeans显示我的错误信息

    public void readFromFile() throws IOException {
        InputStreamReader fr = null;
        try {
            fr = new InputStreamReader(new BufferedReader(new FileInputStream(new FileReader("c:\\cars.txt"))));
            System.out.println(fr.read());
        } catch (Exception ex) {
            System.out.println(ex.getMessage());
        } finally {
            fr.close();
        }
    }  

这种方法有什么问题？

我试图在ArrayList中进行二进制搜索,但binarySearch方法不适用于Long,以及Double和Float.我的代码是

import java.util.*;

 public class BinarySearchInArrayList
 {
     public static void main(String[]args)
     {
         ArrayList<Long> ar = new ArrayList();

         for(long l = 1;l<100000;l++)
         {
             ar.add(l);
         }

         System.out.println("arraylist: "+ar); 
         System.out.println("Which number's index do you want to know? ");
         Scanner scan = new Scanner(System.in);
         int p = scan.nextInt();
         int index = Collections.binarySearch(ar,p);
         System.out.println("number "+p+" has index "+index);
     }

当我使用Integer而不是Long,它工作正常,但我想用它Long.你能帮我吗？