public class Animal {

        private static Animal animal = new Animal();

        public static Animal newInstance() {

                return animal;

        }

}

public class Main {

        public static void main(String[] args) {

                Animal animal =Animal.newInstance();

                System.out.println(animal.hashCode());

        }

}

注：

单例模式就是为了解决要new出来好多好多个对象来，使代码简单化。