public class A { private B b; public void setB(B b){ this.b = b; } }
public class B { private A a; public void setA(A a){ this.a = a; } }
在实际开发中应该尽量避免循环依赖
实例化是:A a = new A();
初始化是:在实例化后调用 a.setB();