java初始化顺序

1、在类的内部，变量定义的先后顺序决定了初始化的顺序，变量会在任何方法（包括构造器）被调用之前得到初始化，而对于静态变量，会首先初始化。

class Bowl {
  Bowl(int marker) {
    System.out.println("Bowl(" + marker + ")");
  }
  void f1(int marker) {
    System.out.println("f1(" + marker + ")");
  }
}

class Cupboard {
  Bowl bowl3 = new Bowl(3);
  static Bowl bowl4 = new Bowl(4);
  Cupboard() {
    System.out.println("Cupboard()");
    bowl4.f1(2);
  }
  void f3(int marker) {
    System.out.println("f3(" + marker + ")");
  }
  static Bowl bowl5 = new Bowl(5);
}

public class StaticInitialization {
  public static void main(String[] args) {
    System.out.println("Creating new Cupboard() in main");
  }
  static Cupboard cupboard = new Cupboard();
}

/*outout如下：

Bowl(4)
Bowl(5)
Bowl(3)
Cupboard()
f1(2)
Creating new Cupboard() in main

*/

//运行以上代码，要执行main方法，则必须先加载StaticInitialization.java类，
而在StaticInitialization.java类中定义了静态变量cupboard，则会先初始化Cupboard类，而Cupboard类中包含静态对象Bowl4、Bowl5，则会先加载Bowl类，输出Bowl(4)
Bowl(5) ，而Cupboard类中还定义了非静态变量bowl3，则输出Bowl(3)，至此Cupboard中的变量初始化完毕，初始化其构造方法，输出Cupboard()
f1(2)，至此StaticInitialization.java类中定义的静态变量cupboard所涉及到的内容初始化完毕，继续执行main方法中的内容，输出Creating new Cupboard() in main。