如何从文件内容创建Java字符串？

我已经用下面这个成语有一段时间了。这似乎是传播最广的，至少在我访问过的网站上。

在Java中有没有更好/不同的方法将文件读入字符串？

private String readFile(String file) throws IOException {
    BufferedReader reader = new BufferedReader(new FileReader (file));
    String         line = null;
    StringBuilder  stringBuilder = new StringBuilder();
    String         ls = System.getProperty("line.separator");

    try {
        while((line = reader.readLine()) != null) {
            stringBuilder.append(line);
            stringBuilder.append(ls);
        }

        return stringBuilder.toString();
    } finally {
        reader.close();
    }
}

当前回答

基于扫描仪的非常精简的解决方案：

Scanner scanner = new Scanner( new File("poem.txt") );
String text = scanner.useDelimiter("\\A").next();
scanner.close(); // Put this call in a finally block

或者，如果要设置字符集：

Scanner scanner = new Scanner( new File("poem.txt"), "UTF-8" );
String text = scanner.useDelimiter("\\A").next();
scanner.close(); // Put this call in a finally block

或者，使用trywithresources块，它将为您调用scanner.close（）：

try (Scanner scanner = new Scanner( new File("poem.txt"), "UTF-8" )) {
    String text = scanner.useDelimiter("\\A").next();
}

请记住，Scanner构造函数可以引发IOException。不要忘记导入java.io和java.util。

来源：Pat Niemeyer的博客

2011-09-16 20:02:17

其他回答

基于扫描仪的非常精简的解决方案：

Scanner scanner = new Scanner( new File("poem.txt") );
String text = scanner.useDelimiter("\\A").next();
scanner.close(); // Put this call in a finally block

或者，如果要设置字符集：

Scanner scanner = new Scanner( new File("poem.txt"), "UTF-8" );
String text = scanner.useDelimiter("\\A").next();
scanner.close(); // Put this call in a finally block

或者，使用trywithresources块，它将为您调用scanner.close（）：

try (Scanner scanner = new Scanner( new File("poem.txt"), "UTF-8" )) {
    String text = scanner.useDelimiter("\\A").next();
}

请记住，Scanner构造函数可以引发IOException。不要忘记导入java.io和java.util。

来源：Pat Niemeyer的博客

2011-09-16 20:02:17

同一主题上有一个变体，它使用for循环而不是while循环来限制行变量的范围。是否“更好”取决于个人品味。

for(String line = reader.readLine(); line != null; line = reader.readLine()) {
    stringBuilder.append(line);
    stringBuilder.append(ls);
}

2008-11-28 20:33:13

使用前面评论中提到的BufferedReader，但这种方式更可读：

String FILE_PATH = "filepath.txt";

try (FileReader fileReader = new FileReader(FILE_PATH)) {
    BufferedReader fileBufferReader = new BufferedReader(fileReader);
    String text = fileBufferReader.lines()
        .collect(Collectors.joining(System.lineSeparator()));
    System.out.println(text);
} catch (IOException e) {
    // exception handling
}

2023-01-24 02:38:59

将文件读取为二进制文件并在末尾转换

public static String readFileAsString(String filePath) throws IOException {
    DataInputStream dis = new DataInputStream(new FileInputStream(filePath));
    try {
        long len = new File(filePath).length();
        if (len > Integer.MAX_VALUE) throw new IOException("File "+filePath+" too large, was "+len+" bytes.");
        byte[] bytes = new byte[(int) len];
        dis.readFully(bytes);
        return new String(bytes, "UTF-8");
    } finally {
        dis.close();
    }
}

2010-04-18 07:34:29

我还不能评论其他条目，所以我就把它留在这里。

这里最好的答案之一(https://stackoverflow.com/a/326448/1521167):

private String readFile(String pathname) throws IOException {

File file = new File(pathname);
StringBuilder fileContents = new StringBuilder((int)file.length());
Scanner scanner = new Scanner(file);
String lineSeparator = System.getProperty("line.separator");

try {
    while(scanner.hasNextLine()) {        
        fileContents.append(scanner.nextLine() + lineSeparator);
    }
    return fileContents.toString();
} finally {
    scanner.close();
}
}

仍然有一个缺陷。它总是在字符串末尾添加换行符，这可能会导致一些奇怪的错误。我的建议是将其更改为：

    private String readFile(String pathname) throws IOException {
    File file = new File(pathname);
    StringBuilder fileContents = new StringBuilder((int) file.length());
    Scanner scanner = new Scanner(new BufferedReader(new FileReader(file)));
    String lineSeparator = System.getProperty("line.separator");

    try {
        if (scanner.hasNextLine()) {
            fileContents.append(scanner.nextLine());
        }
        while (scanner.hasNextLine()) {
            fileContents.append(lineSeparator + scanner.nextLine());
        }
        return fileContents.toString();
    } finally {
        scanner.close();
    }
}

2013-12-13 09:33:32

如何从文件内容创建Java字符串？

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