7.9 初始化及类的加载

• 初次使用之处就是static域初始化发生的地方；
• 所有的static对象和static代码段都会在类加载的时候，依照定义的顺序进行依次初始化。
• 且static修饰的只执行一次。 ```java

class Insect { private int i = 9; protected int j;

Insect() { System.out.println(“i = “ + i + “, j = “ + j); j = 39; }

private static int x1 = printInit(“static Insect.x1 initialized”);

static int printInit(String s) { System.out.println(s); return 47; } }

public class Beetle extends Insect { private int k = printInit(“Beetle.k initialized”);

public Beetle() { System.out.println(“k = “ + k); System.out.println(“j = “ + j); }

private static int x2 = printInit(“static Beetle.x2 initialized”);

public static void main(String[] args) { System.out.println(“Beetle constructor”); Beetle b = new Beetle(); } }

**对于基类、扩展类的static域来说，都是优先于普通域和构造器的执行**
```java
class Flag{
  Flag(String s){
    System.out.println("Flag("+s+")");
  }
}
class Art {
  static Flag flag = new Flag("art");
  Flag f = new Flag("withoutFlag-arg");
  Art(){
    System.out.println("Art()");
  }
}
class Drawing extends Art{
  static Flag flag = new Flag("drawing");
  Flag f = new Flag("withoutFlag-drawing");
  Drawing(){
    System.out.println("Drawing()");
  }
}
public class Cartoon extends Drawing{
  //在导出类中包含对父类的一个引用
  /*Cartoon(){
    System.out.println("Cartoon()");
  }*/
  public static void main(String[] args) {
    new Cartoon();
  }
}