java - 在Java中读/写数字——转换时出现NumberFormatException

Question

我有一个以 UTF-8 格式写入的数字，然后将其读回(稍后阶段)。然后我将其转换为数字，因为我使用该数字进行算术。我收到 NumberFormatException 但看不到原因。我完全以 UTF-8 进行操作，两种方式都有问题吗？

所以，第一个输出很好，我看到了我的号码(作为字符串)。第二个输出失败并出现 NumberFormatException。

这是我用于写入和读取文件的代码:

static public void putContents(File aFile, String content, boolean append) {

    // init
    Writer writer = null;

    // make sure file exists
    if (!aFile.exists()) {
        Util.createFile(aFile.getAbsolutePath());
    }

    // write content
    try {
        writer = new BufferedWriter(new OutputStreamWriter(
                new FileOutputStream(aFile), "UTF-8"));
        writer.write(content);
        writer.close();
    } catch (IOException e) {
        logger.error("Error writing content to file: " + aFile);
    } finally {
        try {
            // Close the writer regardless of what happens
            writer.close();
        } catch (Exception e) {
            logger.error("Error while closing file: " + aFile.getAbsolutePath());
        }
    }

}

static public void createFile(String filename) {

    // protection against accidental overwrite
    if (new File(filename).exists()) {
        logger.warn("File '" + filename + "' already exists. Nothing done.");
        return;
    }

    // create file with directory structure
    File targetFile = new File(filename);
    File parent = targetFile.getParentFile();
    if (!parent.exists() && !parent.mkdirs()) {
        throw new IllegalStateException("Couldn't create dir: " + parent);
    }

    try {
        targetFile.createNewFile();
    } catch (IOException e){
        logger.error("Error while creating empty file '" + filename + "': " + e.getMessage());
    }

}

static public String getContents(File aFile) {

    StringBuilder contents = new StringBuilder();

    try {
        // extract all text from this file
        BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream(aFile), "UTF-8"));
        try {

            String line = null; //not declared within while loop
            while ((line = reader.readLine()) != null) {
                contents.append(line);
                contents.append(System.getProperty("line.separator"));
            }
        } finally {
            reader.close();
        }
    } catch (IOException ex) {
        ex.printStackTrace();
    }

    return contents.toString();
}

这里是我如何生成异常:

public static void main(String[] args) {

    putContents(new File("D:/TEST.TXT"), "122", false);
    String numberString = Util.getContents(new File("D:/TEST.TXT"));

    logger.info("String: " + numberString);
    logger.info("String converted to number: " + Integer.parseInt(numberString));

}

此处输出:

16:28:05,109 INFO  [main] [Util] String: 122
Exception in thread "main" java.lang.NumberFormatException: For input string: "122"
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
at java.lang.Integer.parseInt(Integer.java:492)
at java.lang.Integer.parseInt(Integer.java:527)
at at.tuwien.mucke.util.Util.main(Util.java:154)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120)

Process finished with exit code 1

Answer 1

方法 getContents 在返回值中添加新行。这导致该方法返回 122\r\n

contents.append(System.getProperty("line.separator"));

如果你想删除新行，可以使用:

System.out.println("String converted to number: " + Integer.parseInt(numberString.replaceAll("\r\n", "")));

或者你可以使用

System.out.println("String converted to number: " + Integer.parseInt(numberString.replaceAll("\\s", "")));

这将从返回的数字中删除所有空白字符(由正则表达式元字符 \s 表示)。