Java 中的文件读写有如下几个类

读文件类

FileReader

InputStreamReader

BufferedReader

FileReader可以直接读文件， new FileReader(new File("file.name"))

InputStreamReader 得先创建FileInputStream 类    new InputStreamReader(new FileInputStream(new File("file.name")))

BufferedReader 的构造参数是InputStreamReader   new BufferedReader(new InputStreamReader(new FileInputStream(new File("file.name"))))

写文件

FileWriter

OutputStreamWriter

BufferedWriter

PrintWriter

FileWriter可以直接读文件， new FileWriter(new File("file.name"))

OutputStreamWriter得先创建FileOutputStream 类    new OutputStreamWriter(new FileOutputStream(new File("file.name")))

BufferedWriter的构造参数是OutputStreamWriternew BufferedWriter(new OutputStreamWriter(new FileOutputStream(new File("file.name"))))

PrintWriter的构造参数很多。可以直接是File，也可以是writer

具体怎么用，还请参照Java API

java File 文件读写