以下代码所用到的是单例模式的(     )加载方式？
代码：

public class TestSingletton {
                public static void main(String[] args){
                    ClassA ca = ClassA.newInstance();
                }
}
class ClassA {
                private static ClassA instance=new ClassA();
                public static ClassA newInstance(){
                    return instance;
                }
                private ClassA(){}
}