App showing OS launching activity on the stack after crash.

activity_my.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    tools:context=".MyActivity">

    <TextView
        android:text="@string/hello_world"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

    <Button
        android:id="@+id/launch_main"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:text="@string/launch_main"/>

    <Button
        android:id="@+id/launch_b"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:text="@string/launch_b"
        android:layout_below="@id/launch_main"/>

    <Button
        android:id="@+id/doit"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:text="Do It"
        android:layout_below="@id/launch_b"/>


</RelativeLayout>

BActivity.java

public class BActivity extends Activity implements View.OnClickListener {

    private Button mLaunchMainButton;
    private Button mLaunchBButton;
    private Button mDoIt;
    @Override protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.e("bActivity", "otCreate");
        setContentView(R.layout.activity_my);
        mLaunchMainButton = (Button) findViewById(R.id.launch_main);
        mLaunchBButton = (Button) findViewById(R.id.launch_b);
        mDoIt = (Button) findViewById(R.id.doit);

        mLaunchMainButton.setOnClickListener(this);
        mLaunchBButton.setOnClickListener(this);
        mDoIt.setOnClickListener(this);
    }

    @Override protected void onResume() {
        super.onResume();
        Log.e("bActivity", "onResume");
    }

    public void doIt(View view) {
        String[] strings = { "a", "b", "c" };

        for(int i = 0; i<= strings.length; i++) {
            String x = strings[i];
        }
    }

    @Override public void onClick(View v) {
        int viewId = v.getId();
        switch(viewId) {
            case R.id.launch_main:
                Intent mainIntent = new Intent(this, MyActivity.class);
                startActivity(mainIntent);
                break;
            case R.id.launch_b:
                Intent bIntent = new Intent(this, BActivity.class);
                startActivity(bIntent);
                break;
            case R.id.doit:
                doIt(v);
                break;
        }
    }
}

MyActivity.java

public class MyActivity extends Activity implements View.OnClickListener {
    private Button mLaunchMainButton;
    private Button mLaunchBButton;
    private Button mDoIt;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.e("bActivity", "otCreate");
        setContentView(R.layout.activity_my);

        mLaunchMainButton = (Button) findViewById(R.id.launch_main);
        mLaunchBButton = (Button) findViewById(R.id.launch_b);
        mDoIt = (Button) findViewById(R.id.doit);

        mLaunchMainButton.setOnClickListener(this);
        mLaunchBButton.setOnClickListener(this);
        mDoIt.setOnClickListener(this);


    }
    @Override protected void onResume() {
        super.onResume();
        Log.e("bActivity", "onResume");
    }

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

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    public void doIt(View view) {
        String[] strings = { "a", "b", "c" };

        for(int i = 0; i<= strings.length; i++) {
            String x = strings[i];
        }
    }

    @Override public void onClick(View v) {
        int viewId = v.getId();
        switch(viewId) {
            case R.id.launch_main:
                Intent mainIntent = new Intent(this, MyActivity.class);
                startActivity(mainIntent);
            break;
            case R.id.launch_b:
                Intent bIntent = new Intent(this, BActivity.class);
                startActivity(bIntent);
            break;
            case R.id.doit:
                doIt(v);
            break;
        }
    }
}