如何使用java代码读取纯文本文件呢?

对于读取纯文本文件
    使用BufferedReader对象即可读取
 或
借助Apache common中的方法

BufferedReader br = new BufferedReader(new FileReader("file.txt"));
try {
    StringBuilder sb = new StringBuilder();
    String line = br.readLine();

    while (line != null) {
        sb.append(line);
        sb.append(System.lineSeparator());
        line = br.readLine();
    }
    String str = sb.toString();
} finally {
    br.close();
}

Java7及以后版本可简写try with resources自动关闭连接

try(BufferedReader br = new BufferedReader(new FileReader("file.txt"))) {
    StringBuilder sb = new StringBuilder();
    String line = br.readLine();

    while (line != null) {
        sb.append(line);
        sb.append(System.lineSeparator());
        line = br.readLine();
    }
    String str = sb.toString();
}

Apache Commons IO使用类 IOUtils.toString()

FileInputStream inputStream = new FileInputStream("test.txt");
try {
    String str = IOUtils.toString(inputStream);
} finally {
    inputStream.close();
}

//java7及以后版本

try(FileInputStream inputStream = new FileInputStream("test.txt")) {     
    String str = IOUtils.toString(inputStream);
    
}