How to make transparent status bar in Android

StatusBarUtils.java

public class StatusBarUtils {

    public static void makeTransparentStatusBar(Activity activity) {
        if (Build.VERSION.SDK_INT >= 19 && Build.VERSION.SDK_INT < 21) {
            setWindowFlag(activity, true);
        }
        if (Build.VERSION.SDK_INT >= 19) {
            activity.getWindow().getDecorView().setSystemUiVisibility(View.SYSTEM_UI_FLAG_LAYOUT_STABLE | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN);
        }
        //make fully Android Transparent Status bar
        if (Build.VERSION.SDK_INT >= 21) {
            setWindowFlag(activity, false);
            activity.getWindow().setStatusBarColor(Color.TRANSPARENT);
        }
    }

    private static void setWindowFlag(Activity activity, boolean on) {
        Window win = activity.getWindow();
        WindowManager.LayoutParams winParams = win.getAttributes();
        if (on) {
            winParams.flags |= WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS;
        } else {
            winParams.flags &= ~WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS;
        }
        win.setAttributes(winParams);
    }
}