判断是否只读，可用file.canwrite().

      2. 当要设置是否是可读或者是隐藏时，在java中除了提供file.setreadonly()外，就无其他方法了。

          所以我们必须到dos环境下去设置，在java中用runtime.getruntime().exec("attrib " + """ + file.getabsolutepath() + """+ " +r")该方法可以实现。因为路径file.getabsolutepath()中可能会还有空格，所以必须用引号把它括起来，当作一个参数。这样就可以实现了

(1)   设置只读runtime.getruntime().exec("attrib " + """ + file.getabsolutepath() + """+ " +r");

(2)   设置可写runtime.getruntime().exec("attrib " + """ + file.getabsolutepath() + """+ " -r");

(3)   设置隐藏runtime.getruntime().exec("attrib " + """ + file.getabsolutepath() + """+ " +h");

(4)   设置非隐藏runtime.getruntime().exec("attrib " + """ + file.getabsolutepath() + """+ " -h");

 

   3.对于读写文件的一些操作源代码

      package filecontrol;

 

import java.io.bufferedreader;

import java.io.bufferedwriter;

import java.io.file;

import java.io.filereader;

import java.io.filewriter;

import java.io.ioexception;

import java.io.randomaccessfile;

 

public class filecontrol {

            private static string filename;

            private static file file;

            public static void main(string[] args) {

                        try {

                                    filename = "exercise.java";

                                    file = new file("e:" + "", filename);

                                    if (file.exists()) {

//                                              file.delete();

                                    } else {

                                                file.createnewfile();

                                    }

                                   

                                    if (file.isdirectory()) {

                                                system.out.println("this file is directory");

                                    }

                                   

                                    if (file.isfile()) {

                                                system.out.println("this file is a file");

                                    }

                                   

                                   

                                    filewriter fw = new filewriter("e:" + "" + filename);

                                    // 缓冲写入文件，并且可以通过转义符或是bw.newline();来换行

 

                                    bufferedwriter bw = new bufferedwriter(fw);

//                                  将字符串写入文件

                                    bw.write(" 大家好！");

                                    bw.newline();

                                    bw.write("本?是《jsp?程技巧》");

                                    bw.newline();

                                    bw.write("?多多指教！");

                                    bw.newline();

                                    bw.write("email:stride@sina.comqianyf");

                                    bw.flush();

                                    bw.close();

 

                                    //在文件制定位置追加内容

                                    randomaccessfile rf = new randomaccessfile("e:" + "" + filename, "rw");

                                    rf.seek(rf.length());

                                    rf.writebytes(" zui jia  de");

                                    rf.close();

                                   

                                    // 通过缓冲来读文件

                                    filereader fr = new filereader("e:" + "" + filename);

                                    bufferedreader br = new bufferedreader(fr);

                                    string linedata = br.readline();

                                    while (null != linedata) {

                                                system.out.println(linedata);

                                                linedata = br.readline();

                                    }

                                   

                                               

                      } catch (ioexception ee) {

                                    system.out.println("system exception");

                      }

                       

            }

 

}