android how to start a new activity on button click

1Intent intent = new Intent(this, DisplayMessageActivity.class);
2        intent.putExtra(key:,value:);
3        startActivity(intent);

1Intent intent = new Intent(this, ActivityToBeCalled.class);
2startActivity(intent);

1 private Button button;
2
3    @Override
4    protected void onCreate(Bundle savedInstanceState) {
5        super.onCreate(savedInstanceState);
6        setContentView(R.layout.activity_main4);
7        button = (Button)findViewById(R.id.button7);
8
9        button.setOnClickListener(new View.OnClickListener() {
10            @Override
11            public void onClick(View v) {
12                openInsideActivity4();
13            }
14        });
15    }
16    public void openInsideActivity4()
17    {
18        Intent intent = new Intent(this,InsideActivity4.class);
19        startActivity(intent);
20    }