java从文件中读取数据的六种方法

Java从文件中读取数据的六种方法

在Java应用程序中，从文件中读取数据是一个常见的操作。这篇文章将为大家介绍Java读取文件的六种方法，帮助大家学习如何读取文件数据。

方法1：使用 FileInputStream

FileInputStream fileInputStream = null;
try {
    File file = new File("file.txt");
    fileInputStream = new FileInputStream(file);
    int content;
    while ((content = fileInputStream.read()) != -1) {
        System.out.print((char) content);
    }
} catch (IOException e) {
    e.printStackTrace();
} finally {
    try {
        if (fileInputStream != null) {
            fileInputStream.close();
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

方法2：使用 BufferedReader 和 FileReader

BufferedReader bufferedReader = null;
try {
    File file = new File("file.txt");
    FileReader fileReader = new FileReader(file);
    bufferedReader = new BufferedReader(fileReader);
    String line;
    while ((line = bufferedReader.readLine()) != null) {
        System.out.println(line);
    }
} catch (IOException e) {
    e.printStackTrace();
} finally {
    try {
        if (bufferedReader != null) {
            bufferedReader.close();
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

方法3：使用 RandomAccessFile

RandomAccessFile randomAccessFile = null;
try {
    randomAccessFile = new RandomAccessFile("file.txt", "r");
    String line = null;
    while ((line = randomAccessFile.readLine()) != null) {
        System.out.println(line);
    }
} catch (IOException e) {
    e.printStackTrace();
} finally {
    try {
        if (randomAccessFile != null) {
            randomAccessFile.close();
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

方法4：使用 Scanner

Scanner scanner = null;
try {
    scanner = new Scanner(new File("file.txt"));
    while (scanner.hasNext()) {
        System.out.println(scanner.nextLine());
    }
} catch (FileNotFoundException e) {
    e.printStackTrace();
} finally {
    if (scanner != null) {
        scanner.close();
    }
}

方法5：使用 Files 类的 readAllBytes 方法

try {
    byte[] bytes = Files.readAllBytes(Paths.get("file.txt"));
    System.out.println(new String(bytes));
} catch (IOException e) {
    e.printStackTrace();
}

方法6：使用 Files 类的 readAllLines 方法

try {
    List<String> lines = Files.readAllLines(Paths.get("file.txt"));
    for (String line : lines) {
        System.out.println(line);
    }
} catch (IOException e) {
    e.printStackTrace();
}

以上就是Java从文件中读取数据的六种方法，我们可以根据需求选择方法进行文件读取。

下面是一个使用BufferedReader的示例：

public static void main(String[] args) {
    BufferedReader bufferedReader = null;
    try {
        File file = new File("file.txt");
        FileReader fileReader = new FileReader(file);
        bufferedReader = new BufferedReader(fileReader);
        String line;
        while ((line = bufferedReader.readLine()) != null) {
            System.out.println(line);
        }
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        try {
            if (bufferedReader != null) {
                bufferedReader.close();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

下面是一个使用Scanner的示例：

public static void main(String[] args) {
    Scanner scanner = null;
    try {
        scanner = new Scanner(new File("file.txt"));
        while (scanner.hasNext()) {
            System.out.println(scanner.nextLine());
        }
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } finally {
        if (scanner != null) {
            scanner.close();
        }
    }
}