Question

我尝试使用java读取和写入文件。我已经尝试了我的代码，但它无法正常工作。

见下面是我的代码：

import java.util.*;
import java.io.*;

public class UptimeSample {


    public static void main(String[] args) {
        try
        {
            double oldTime=0;
            BufferedReader read=new BufferedReader(new FileReader("C:/eGurkha/agent/sample/UptimeRecord.txt"));
            String oldline=read.readLine();
            if(oldline == null)
            {
                System.out.println("New Entry ::::");
                Process p=Runtime.getRuntime().exec("C:\\eGurkha\\lib\\vmgfiles\\win\\VmgUptimeTest.exe");
                BufferedReader rd=new BufferedReader(new InputStreamReader(p.getInputStream()));
                String line=rd.readLine();
                System.out.println(line);
                String[] word=line.split("=");
                FileWriter fileWriter=new FileWriter("C:/eGurkha/agent/sample/UptimeRecord.txt");
                fileWriter.write(word[1]);
                System.out.println("New System Time is :"+word[1]);
                System.out.println("String Written");
            }
            else
            {
                oldTime=Double.parseDouble(oldline);
                Process p=Runtime.getRuntime().exec("C:\\eGurkha\\lib\\vmgfiles\\win\\VmgUptimeTest.exe");
                BufferedReader rd=new BufferedReader(new InputStreamReader(p.getInputStream()));
                String line=rd.readLine();
                String[] word=line.split("=");
                FileWriter fileWriter=new FileWriter("C:/eGurkha/agent/sample/UptimeRecord.txt");
                fileWriter.write(word[1]);
                System.out.println("New System Time is :"+word[1]);
                System.out.println("String Written");
                double crrTime=Double.parseDouble(word[1]);
                double diffTime=crrTime-oldTime;
                System.out.println("Difference Time is :"+diffTime);
            }
        }
        catch(IOException e)
        {
            e.printStackTrace();
        }

    }

}

它提供以下输出：

New Entry ::::
System=13042.827175
New System Time is :13042.827175
String Written

输出正确，但问题是当我打开＆＃34; UptimeRecord.txt＆＃34;文件，文件为空。我无法写入该文件。

Answer 1

您需要.flush()和.close() FileWriter。当flush FileWriter时，数据被发送到其目的地。您还可以考虑使用BufferedFileWriter来处理冲洗和关闭。

另请参阅：difference between flush and close function in case of filewriter in java

Answer 2

您需要关闭FileWriter

fileWriter.close();

根据JoeBlade的建议，这应该在finally块中完成：

} catch (IOException e){
    e.printStackTrace();
} finally {
    if (fileWriter != null) {
        fileWriter.close();
    }
}

Answer 3

文件必须关闭file.close()

fileWriter.close();

我不能在文本中写一个字符串

3 个答案: