Switch to Front Camera and Back Camera not working

Question

My application freezes when I call switchCam method in my code.something must be wrong there, but i cant understand what is the problem.Can someone help me out there what is the actual problem in my code.

public class MainActivity extends AppCompatActivity {
private Camera mCamera = null;
SurfaceHolder surfaceHolder=null;
private CameraView mCameraView = null;
int currentCameraId = 0;

@Override
protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
            WindowManager.LayoutParams.FLAG_FULLSCREEN);//int flag, int mask

    openCam();
    //setCameraDisplayOrientation(MainActivity.this, currentCameraId, mCamera);

}

public void openCam() {
    try {
        mCamera = Camera.open();//you can use open(int) to use different cameras
    } catch (Exception e) {
        Log.d("ERROR", "Failed to get camera: " + e.getMessage());
        mCamera = Camera.open();//you can use open(int) to use different cameras
    }
    if (mCamera != null) {
        mCameraView = new CameraView(this, mCamera);//create a SurfaceView to show camera data
        FrameLayout camera_view = (FrameLayout) findViewById(R.id.camera_preview);
        camera_view.addView(mCameraView);//add the SurfaceView to the layout
    }

}

public void switchCam(View view){
    int camNum = 0;
    camNum = Camera.getNumberOfCameras();
    int camBackId = Camera.CameraInfo.CAMERA_FACING_BACK;
    int camFrontId = Camera.CameraInfo.CAMERA_FACING_FRONT;
    Toast.makeText(getApplicationContext(),"Hi Cam"+camNum,Toast.LENGTH_SHORT).show();
    Camera.CameraInfo currentCamInfo = new Camera.CameraInfo();

    //if camera is running
    if (mCamera != null){
        //and there is more than one camera
       mCamera.stopPreview();
        mCamera.release();

        //swap the id of the camera to be used
        if(currentCameraId == Camera.CameraInfo.CAMERA_FACING_BACK){
            currentCameraId = Camera.CameraInfo.CAMERA_FACING_FRONT;
        }
        else {
            currentCameraId = Camera.CameraInfo.CAMERA_FACING_BACK;
        }
        mCamera = Camera.open(currentCameraId);

        //setCameraDisplayOrientation(MainActivity.this, currentCameraId, mCamera);
        try {
            mCamera.setPreviewDisplay(surfaceHolder);
        } catch (IOException e) {
            e.printStackTrace();
        }
        mCamera.startPreview();
    }

}

CameraView class is here

public class CameraView extends SurfaceView implements SurfaceHolder.Callback{
private SurfaceHolder mHolder;
private Camera mCamera;
int currentCameraId=0;
public CameraView(Context context, Camera camera) {
    super(context);
    mCamera = camera;
    //get the holder and set this class as the callback, so we can get camera data here
    mHolder = getHolder();
    mHolder.addCallback(this);
    mHolder.setType(SurfaceHolder.SURFACE_TYPE_NORMAL);
}

@Override
public void surfaceCreated(SurfaceHolder surfaceHolder) {
    try {
        mCamera.setPreviewDisplay(surfaceHolder);
        mCamera.startPreview();
    }catch (IOException e) {
        Log.d("ERROR", "Camera error on surfaceCreated " + e.getMessage());
    }
}

@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {

    mCamera.startPreview();

    if(mHolder.getSurface() == null)//check if the surface is ready to receive camera data
        return;
    try{
        mCamera.stopPreview();
    } catch (Exception e){
        //this will happen when you are trying the camera if it's not running
    }
    try{
        mCamera.setPreviewDisplay(mHolder);
        mCamera.startPreview();
    } catch (IOException e) {
        Log.d("ERROR", "Camera error on surfaceChanged " + e.getMessage());
    }
}

@Override
public void surfaceDestroyed(SurfaceHolder holder) {
    mCamera.stopPreview();
    mCamera.release();
}

}

It will be my very pleasure if you share any link with me that can help me out for taking picture too .Thanks in advance :)