How to create a button that open a new activity in android - انشاء زر تستطيع من خلاله فتح نافذة جديدة

How to create a button that open a new activity in android :

Java:

rotected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);


    Button start = (Button)findViewById(R.id.Strat);
    start.setOnClickListener(new View.OnClickListener() {
        @Override        public void onClick(View v) {
            Intent i = new Intent(MainActivity.this,dept.class);
            startActivity(i);
        }
    });

XML: 

<LinearLayout    android:layout_width="match_parent"    android:layout_height="wrap_content"    android:gravity="center"    android:orientation="vertical">

 <Button        android:id="@+id/Strat"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_marginTop="70dp"        android:background="@drawable/start"        android:paddingLeft="125dp"        android:paddingRight="125dp"        android:textAlignment="center"        android:textColor="@color/colorewhite"        android:textSize="25sp" />

</LinearLayout>