创建多级文件夹/目录下的文件

创建多级文件夹下的文件，一定是先有文件夹再有文件，即在父目录的基础上创建子目录/文件

几个关键的方法：

File  genfile=new File(父文件,"子文件");

xxxxx.mkdirs();//创建目录

xxxxx.createNewFile();

public class MainActivity extends AppCompatActivity {    // Storage Permissions    private static final int REQUEST_EXTERNAL_STORAGE = 1;    private static String[] PERMISSIONS_STORAGE = {Manifest.permission.READ_EXTERNAL_STORAGE, Manifest.permission.WRITE_EXTERNAL_STORAGE};    private Button button;    String BASE_FILE_PATH="/storage/emulated/0";    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        verifyStoragePermissions(this);//        File genFile= Environment.getExternalStorageDirectory();//        System.out.println("genFile="+genFile);//genFile=/storage/emulated/0        File  genfile=new File(BASE_FILE_PATH,"lcj");        if (genfile.exists()){            System.out.println("lcj 文件夹已经存在");        }else {            genfile.mkdirs();//创建目录        }        //二级文件夹的创建        File secFile=new File(genfile,"原始数据");        if (secFile.exists()){            System.out.println("原始数据 文件夹已经存在");        }else {            secFile.mkdirs();//创建目录        }        FileReader fr=null;        FileWriter fw=null;        FileInputStream fis=null;        FileOutputStream fos=null;        long start = System.currentTimeMillis();        try {             //创建“/storage/emulated/0/lcj/原始数据/2.txt文件              File childFile = new File(secFile,"2.txt");              if (childFile.exists()) {                  Log.e("TAG", "wen  jian   yijing  cun zai");              } else {                  childFile.createNewFile();              }            //创建“/storage/emulated/0/lcj/原始数据/200.txt文件            File childFile2 = new File(secFile,"200.txt");            if (childFile2.exists()) {                Log.e("TAG", "file2  yijing  cun zai");            } else {                childFile2.createNewFile();            }            //输入流指定从 哪个文件去读取数据，这里是从childFile所指定的文件，即2.txt            fr = new FileReader(childFile);            //输出流指定从 把数据写到哪个文件，这里是写到childFile2所指定的文件，即200.txt            fw = new FileWriter(childFile2);            int len;            while ((len = fr.read()) != -1) {//判断读取的长度，不等于-1 即没有读到末尾，继续循环，继续去读                fw.write(len);//把读取到的字符长度写到对fw所指定的文件中，这里为写到200.txt中                System.out.println(fr.read());            }            long end = System.currentTimeMillis();            long total = end - start;            Toast.makeText(MainActivity.this, "ok  了", Toast.LENGTH_SHORT).show();            Log.i("TAG", "总共花费的时间=" + total);        } catch (IOException e) {            e.printStackTrace();        }    }/** *权限检查 */    public static void verifyStoragePermissions(Activity activity) {// Check if we have write permission        int permission = ActivityCompat.checkSelfPermission(activity,                Manifest.permission.WRITE_EXTERNAL_STORAGE);        if (permission != PackageManager.PERMISSION_GRANTED) {// We don't have permission so prompt the user            ActivityCompat.requestPermissions(activity, PERMISSIONS_STORAGE,                    REQUEST_EXTERNAL_STORAGE);        }    }