从一个文本文件读取并写入两个文本文件

Question

我需要读取一个文本文件(carsAndBikes.txt)，在cars.txt或bikes.txt carsAndBikes中的写入包含汽车和自行车的列表，每个名称的第一个字符是C或B (C代表汽车，B代表自行车)。到目前为止，我有，但它显示汽车和自行车的内容。而不是分开的内容。(仅限汽车或仅限自行车)

   public static void separateCarsAndBikes(String filename) throws FileNotFoundException, IOException
    {
        //complete the body of this method to create two text files
        //cars.txt will contain only cars
        //bikes.txt will contain only bikes    
        
        File fr = new File("C:\\Users\\KM\\Documents\\NetBeansProjects\\Question4\\carsAndBikes.txt");
        Scanner scanFile = new Scanner(fr);                                                             
        String line;
                       
        while(scanFile.hasNextLine())
        {
            line = scanFile.nextLine();
            if(line.startsWith("C"))
            {
               
                try(PrintWriter printWriter = new PrintWriter("C:\\Users\\KM\\Documents\\NetBeansProjects\\Question4\\cars.txt"))
                {                  
                   printWriter.write(line);                                                                           
                }
                catch(Exception e)
                {
                    System.out.println("Message" + e);
                }
            }
            else
            {
                
                try(PrintWriter printWriter = new PrintWriter("C:\\Users\\KM\\Documents\\NetBeansProjects\\Question4\\bikes.txt"))
                {                                       
                    printWriter.write(line);                  
                }
                catch(Exception e)
                {
                    System.out.println("Message" + e);
                }               
            }            
        } 
        //close the file
       scanFile.close();      
    }        

Answer 1

您正在检查输入文件名是否以c开头，而不是检查读取行是否以c开头。

您还应该在循环之前打开这两个输出文件，并在循环之后关闭它们。

// Open input file for reading 
File file = new File("C:\\Users\\KM\\Documents\\NetBeansProjects\\Question4\\carsAndBikes.txt");      
BufferedReader br = new BufferedReader(new FileReader(file))); 

// Open bike outputfile for writing
// Open cars outputfile for writing

// loop over input file contents
String line;
while( line = br.readLine()) != null ) {

    // check the start of line for the character
    if (line.startsWith("C") {
        // write to cars
    } else {
        // write to bikes
    }
}

// close all files