public class MainActivity extends AppCompatActivity {

    EditText editAdam;
    Button buttonAdam;
    TextView textAdam;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        editAdam = findViewById(R.id.editadam);
        buttonAdam = findViewById(R.id.buttonadam);
        textAdam = findViewById(R.id.textadam);
    }

    public void OnayAdam(View view)
    {
        int sayiAy = Integer.parseInt(editAdam.getText().toString());
        String ay = "";
        editAdam.setText("");

        switch (sayiAy){
            case 1:
                ay="OCAK";
                break;

            case 2:
                ay="ŞUBAT";
                break;

            case 3:
                ay="MART";
                break;

            case 4:
                ay="NİSAN";
                break;

            case 5:
                ay="MAYIS";
                break;

            case 6:
                ay="HAZİRAN";
                break;

            case 7:
                ay="TEMMUZ";
                break;

            case 8:
                ay="AĞUSTOS";
                break;

            case 9:
                ay="EYLÜL";
                break;

            case 10:
                ay="EKİM";
                break;

            case 11:
                ay="KASIM";
                break;

            case 12:
                ay="ARALIK";
                break;

            default:
                ay="YANLIŞ BİLGİ";
                break;
        }
        textAdam.setText(ay);
    }
}

//////////////////////////////////////////////////

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <EditText
        android:id="@+id/editadam"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_marginStart="50dp"
        android:layout_marginTop="50dp"
        android:hint="La gardas buraya birşeyler yaz."
        />

    <Button
        android:id="@+id/buttonadam"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_below="@+id/editadam"
        android:layout_marginStart="150dp"
        android:layout_marginTop="50dp"
        android:text="Giriş"
        android:onClick="OnayAdam"
        />

    <TextView
        android:id="@+id/textadam"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/buttonadam"
        android:layout_marginTop="300dp"
        android:text="Boş"
        android:layout_centerHorizontal="true"
        android:gravity="center"
        android:textStyle="bold"
        android:textColor="@color/black"
        android:textSize="40dp"
        />

</RelativeLayout>