MainActivity.java

public class MainActivity extends AppCompatActivity {
    static String TAG = "BLEScanner";

    BluetoothAdapter mBluetoothAdapter;
    BluetoothLeScanner mBluetoothLeScanner;

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

        BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
        BluetoothLeScanner mBluetoothLeScanner = mBluetoothAdapter.getBluetoothLeScanner();

        mBluetoothLeScanner.startScan(new ScanCallback() {
            @Override
            public void onScanResult(int callbackType, ScanResult result) {
                super.onScanResult(callbackType, result);
                Log.i(TAG, result.getDevice().toString());
            }

            @Override
            public void onBatchScanResults(List<ScanResult> results) {
                super.onBatchScanResults(results);
            }

            @Override
            public void onScanFailed(int errorCode) {
                super.onScanFailed(errorCode);
                Log.i(TAG, String.valueOf(errorCode));
            }
        });
    }
}