java基础为啥加static就不报错了

public class A {
    A a=new A();

    public static void main(String[] args) {
        A a1 = new A();
    }
}
//Exception in thread "main" java.lang.StackOverflowError

public class A {
  static  A a=new A();

    public static void main(String[] args) {
        A a1 = new A();
    }
}
//不报错
为啥

加载顺序不同，所以需要加static