java printwriter：输出文件为空

Question

问题：如何要求定义的输出class将结果打印在输出文件中作为.txt

所有其他 java classes 似乎都在工作并且运行正常，但它无法在输出文件夹中打印出任何数据。我已导入 PrintWriter，但它不会创建文件

代码：

import java.io.IOException;
 import java.io.PrintWriter;



public class Outputs
{
    //INSTANCE FIELDS

    private Solution cwsSolution;
    private Solution bestSol;

    // CLASS CONSTRUCTOR

    Outputs()
    {   cwsSolution = null;
        bestSol = null;
    }

    // SET METHODS

    public void setCWSSol(Solution cwsSol)
    {   cwsSolution = cwsSol;
    }

    public void setOBSol(Solution obSol)
    {   bestSol = obSol;
    }

    // GET METHODS

    public Solution getCWSSol()
    {   return cwsSolution;
    }

    public Solution getOBSol()
    {   return bestSol;
    }

    //PUBLIC METHOD 
printOutputFile()

    public void sendToFile(String outFile)
    {
        try 
        {   PrintWriter out = new PrintWriter(outFile);
            out.println("***************************************************");
            out.println("*                      OUTPUTS                    *");
            out.println("***************************************************");
            out.println("\r\n");
            out.println("--------------------------------------------");
            out.println("Clarke & Wright Solution (parallel version)");
            out.println("--------------------------------------------");
            out.println(cwsSolution.toString() + "\r\n");
            out.println("--------------------------------------------");
            out.println("\r\n OUR BEST SOLUTION:\r\n");
            out.println("--------------------------------------------");
            out.println(bestSol.toString() + "\r\n");
            out.close();
        } catch (IOException exception) 
        {   System.out.println("Error processing output file: " + exception);
        }
    }
}

Answer 1

我看到的问题是您忘记了 .flush() 和 PrintWriter 在关闭它之前明确地将数据发送到输出目标。

[...]
out.println(bestSol.toString() + "\r\n");
out.flush();
out.close();
[...]

Answer 2

我使用 sendToFile() 创建了一个虚拟程序，它工作正常并创建了一个输出文件。

请粘贴您遇到的错误。我希望你正确地初始化了变量 "cwsSolution" 和 "cwsSolution" 并且没有抛出 null。

请查看以下link是否有帮助： How to use PrintWriter and File classes in Java?

示例代码如下：

   public class Outputs
 {
    String bestSol="bestSol";
    String cwsSolution="cwsSolution";

   public void sendToFile(String outFile)
   {

   try 
   {   PrintWriter out = new PrintWriter(outFile);
       out.println("***************************************************");
       out.println("*                      OUTPUTS                    *");
       out.println("***************************************************");
       out.println("\r\n");
       out.println("--------------------------------------------");
       out.println("Clarke & Wright Solution (parallel version)");
       out.println("--------------------------------------------");
       out.println(cwsSolution.toString() + "\r\n");
       out.println("--------------------------------------------");
       out.println("\r\n OUR BEST SOLUTION:\r\n");
       out.println("--------------------------------------------");
       out.println(bestSol.toString() + "\r\n");
       out.close();
   } catch (IOException exception) 
   {   System.out.println("Error processing output file: " + exception);
   }
 }

   public static void main(String[] args) {
        Outputs output = new Outputs();
        output.sendToFile("C:\t.txt");
   }
}

java printwriter：输出文件为空

java printwriter: Output file empty

java

filepath

printwriter