继承与初始化(static对象初始化顺序)

程序如下：

class Insect extends father {

  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 test extends Insect {

  private int k = printInit("Beetle.k initialized");

  public test() {

 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");

    // test b = new test();

  }

} 

output：

static Insect.x1 initialized

static Beetle.x2 initialized

Beetle constructor

将   // test b = new test();注释取消之后 output：

static Insect.x1 initialized

static Beetle.x2 initialized

Beetle constructor

i = 9, j = 0

Beetle.k initialized

k = 47

j = 39

要点 ：在对better类加载过程中，编译器注意到有一个基类，于是对基类进行加载，不管是否打算产生一个该基类的对象，这都要发生。加载过程是最先执行的，static对象是在加载过程中创建的，所以先输出前两句。