final CameraManager cm = (CameraManager) context.getSystemService(Context.CAMERA_SERVICE);
for(String camera: cm.getCameraIdList()) {
    cm.openCamera(camera, new CameraDevice.StateCallback() {
        @Override
        public void onOpened(CameraDevice camera) {
            // Camera is available
            // Do some stuff ...
            
            camera.close();
        }

        @Override
        public void onDisconnected(CameraDevice camera) {
            // Camera is unavailable
            // Do some stuff ...
        }

        @Override
        public void onError(CameraDevice camera, int error) {
            // Camera is unavailable
            // Do some stuff ...
        }
    }, null);
}