Andoid - добавление Activity \ переключение между Activity

MainActivity.java
public class MainActivity extends Activity {

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

Button swith = (Button)findViewById(R.id.button1);
Button swith3 = (Button)findViewById(R.id.button3);
swith.setOnClickListener(new OnClickListener()

{

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Intent SecAct = new Intent(getApplicationContext(), SecondActivity.class);
Intent SecAct2 = new Intent(getApplicationContext(), SecondActivity2.class);
startActivity(SecAct);
startActivity(SecAct2);
}
});

swith3.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent threActivity = new Intent(MainActivity.this, SecondActivity2.class);
startActivity(threActivity);
}
});
}




@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}

}