BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); String file1 = reader.readLine(); String file2 = reader.readLine(); FileInputStream fis1 = new FileInputStream(file1); FileInputStream fis2 = new FileInputStream(file2); FileOutputStream fos1 = new FileOutputStream(file1, true); while (fis2.available() > 0) { int count2 = fis2.read(); fos1.write(count2); } while (fis1.available() > 0) { int count1 = fis1.read(); fos1.write(count1); } fis2.close(); fis1.close(); fos1.close(); }