java - BufferedReader 不复制文件

Question

我编写了下面的代码来复制文件及其内容。

static void copyFile(File inFile, String destination) {
    if (inFile.isFile()) {
        try {
            String str = destination + "//" + inFile.getName();

            BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(inFile),"UTF-8"));
            BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(new File(str), false), "UTF-8"));

            String line;
            try {
                 while((line = br.readLine()) != null) {
                      bw.write(line);
                      System.out.println(line);
                }                  
            } catch (IOException ex) {
                  Logger.getLogger(JavaApplication10.class.getName()).log(Level.SEVERE, null, ex);
            }
        } catch (FileNotFoundException ex) {
            Logger.getLogger(JavaApplication10.class.getName()).log(Level.SEVERE, null, ex);
        } catch (UnsupportedEncodingException ex) {
            Logger.getLogger(JavaApplication10.class.getName()).log(Level.SEVERE, null, ex);
        }
    } else if( inFile.isDirectory()) {
        String str = destination + "\\" + inFile.getName();
        File newDir = new File( str );
        newDir.mkdir();
        for( File file : inFile.listFiles())
            copyFile(file, newDir.getAbsolutePath());
    }
}

代码按预期在目标位置创建文件，但 .txt 文件为空。进入while循环的部分

bw.write(line); 

不起作用

System.out.println(line); 

有效。

Answer 1

您需要关闭您的Writer才能让他刷新流。这可以使用较新的 try with ressources 方法来完成(首选):

String str = destination + "//" + inFile.getName();
// note the paranthesis here, notfing that this is has to be closed after leaving the try block.
try (
    BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(inFile), "UTF-8"));
    BufferedWriter bw = new BufferedWriter(
            new OutputStreamWriter(new FileOutputStream(new File(str), false), "UTF-8"))) {

    String line;
    try {
        while ((line = br.readLine()) != null) {
            bw.write(line);
            System.out.println(line);
        }
    } catch (IOException ex) {
        ex.printStackTrace();
    }
} catch (FileNotFoundException ex) {
    ex.printStackTrace();

} catch (UnsupportedEncodingException ex) {
    ex.printStackTrace();

} catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}

或者使用finally block :

BufferedWriter bw = null;
BufferedReader br = null;
try {
    String str = destination + "//" + inFile.getName();
    br = new BufferedReader(new InputStreamReader(new FileInputStream(inFile), "UTF-8"));
    bw = new BufferedWriter(
            new OutputStreamWriter(new FileOutputStream(new File(str), false), "UTF-8"));

    String line;
    try {
        while ((line = br.readLine()) != null) {
            bw.write(line);
            System.out.println(line);
        }
    } catch (IOException ex) {
        ex.printStackTrace();
    }
} catch (FileNotFoundException ex) {
    ex.printStackTrace();

} catch (UnsupportedEncodingException ex) {
    ex.printStackTrace();

} finally {
    try {
        if(bw != null)
            bw.close();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    try {
        if (br != null)
            br.close();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

此外，IDE 或编译器应该警告您不要关闭它们。