Fail to connect to camera service

 camera = Camera.open(0);

        <uses-permission android:name="android.permission.CAMERA" />
        <uses-feature android:name="android.hardware.camera" />
        <uses-feature android:name="android.hardware.camera.autofocus" />

package com.example.myapplication;
 
import android.annotation.TargetApi;
import android.content.Context;
import android.content.pm.PackageManager;
import android.hardware.Camera;
import android.os.Build;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.widget.Toast;
 
import java.io.IOException;
 
 
public class MainActivity extends ActionBarActivity {
 
    SurfaceView sv;
    SurfaceHolder holder;
    HolderCallback holderCallback;
    Camera camera;
 
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        sv = (SurfaceView) findViewById(R.id.surfaceView);
        holder = sv.getHolder();
        holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
 
        holderCallback = new HolderCallback();
        holder.addCallback(holderCallback);
    }
 
    @TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH)
    @Override
    protected void onResume() {
        super.onResume();
        camera = Camera.open(0);
       // setPreviewSize(FULL_SCREEN);
    }
 
    @Override
    protected void onPause() {
        super.onPause();
        if (camera != null)
            camera.release();
        camera = null;
    }
 
 
 
    class HolderCallback implements SurfaceHolder.Callback {
 
        @Override
        public void surfaceCreated(SurfaceHolder holder) {
            try {
                camera.setPreviewDisplay(holder);
                camera.startPreview();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
 
        @Override
        public void surfaceChanged(SurfaceHolder holder, int format, int width,
                                   int height) {
            camera.stopPreview();
            //setCameraDisplayOrientation(CAMERA_ID);
            try {
                camera.setPreviewDisplay(holder);
                camera.startPreview();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
 
        @Override
        public void surfaceDestroyed(SurfaceHolder holder) {
 
        }
 
    }
}