得到包和类名

public class Main {
    public static void main(String[] argv) {
        Class cls = String.class;
        System.out.println(getPackageAndClassName(cls));
    }

    public static String getPackageAndClassName(Class cls) {
        if (cls != null) {
            StringBuilder builder = new StringBuilder();
            builder.append(cls.getPackage().getName());
            builder.append(".");
            builder.append(cls.getSimpleName());
            return builder.toString();
        }
        return null;
    }
}