Many a times, you want to save some contents permanently from your program. If the data is few words, you can save them in shared preferences. But for larger contents, you need to use a file. To save a file in sdcard, first of all you should have the permission in your app. You should add this line in AndroidManifest.xml file. <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/> Next in code, you should open the file. File fl = new File("/mnt/sdcard/yourdirname","yourfilename"); try { FileWriter wr = new FileWriter(fl); wr.write(str);//str is the string to be written to file wr.close(); } catch (IOException e) { e.printStackTrace(); } For the File constructor, first parameter is directory name and second is filename. It is always better to write to another directory in sdcard. What happens if the directory does not exist? Your program will crash. First ensur...