Use SharedPreference to store value in Application cache
SharedPreference prefs = getSharedPreferences("UserInfo", 0);
SharedPreferences.Editor editor = prefs.edit();
editor.putString("username", username);
editor.putString("password", password);
editor.commit();
when App started Retrieve data from SharedPreference
SharedPreference prefs = getSharedPreferences("UserInfo", 0);
String username = prefs.getString("username","");
String password = prefs.getString("password","");
if cache is cleared SharedPreference also cleared.so you have to make a condition like if username and password empty means not enter Application.