Bundle

to set the value:
Bundle bundle = new Bundle();
            bundle.putString("FLAG", "addbyemail");

            Intent buddylist = new Intent();
            buddylist.setClassName("com.examples", "com.buddylist.AddbyEmail");
            buddylist.putExtras(bundle);

            startActivity(buddylist);

to get the value:
 private Bundle bun;
bun = getIntent().getExtras();
        String username = bun.getString("FLAG");