From here: http://www.anddev.org/working_with_files-t115.html
//Writing a file... try { // catches IOException below final String TESTSTRING = new String("Hello Android"); /* We have to use the openFileOutput()-method * the ActivityContext provides, to * protect your file from others and * This is done for security-reasons. * We chose MODE_WORLD_READABLE, because * we have nothing to hide in our file */ FileOutputStream fOut = openFileOutput("samplefile.txt", MODE_PRIVATE); OutputStreamWriter osw = new OutputStreamWriter(fOut); // Write the string to the file osw.write(TESTSTRING); /* ensure that everything is * really written out and close */ osw.flush(); osw.close(); //Reading the file back... /* We have to use the openFileInput()-method * the ActivityContext provides. * Again for security reasons with * openFileInput(...) */ FileInputStream fIn = openFileInput("samplefile.txt"); InputStreamReader isr = new InputStreamReader(fIn); /* Prepare a char-Array that will * hold the chars we read back in. */ char[] inputBuffer = new char[TESTSTRING.length()]; // Fill the Buffer with data from the file isr.read(inputBuffer); // Transform the chars to a String String readString = new String(inputBuffer); // Check if we read back the same chars that we had written out boolean isTheSame = TESTSTRING.equals(readString); Log.i("File Reading stuff", "success = " + isTheSame); } catch (IOException ioe) {ioe.printStackTrace();}