Java类中字段和方法的初始化顺序（包含static）

Java类中字段和方法的初始化顺序（包含static）

<span style="font-family:Times New Roman;font-size:14px;">package cm.java.Practic5;

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

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

class Table {
  static Bowl bowl1 = new Bowl(1);

  Table() {
    System.out.println("Table()");
    bowl2.f1(1);
  }

  void f2(int marker) {
    System.out.println("f2(" + marker + ")");
  }

  static Bowl bowl2 = new Bowl(2);
}

class Cupboard {
  Bowl bowl3 = new Bowl(3);
  static Bowl bowl4 = new Bowl(4);

  public 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 InitRelatedP95 {
  public static void main(String[] args) {
    System.out.println("Creating new cupboard() in main");
    new Cupboard();
    System.out.println("Creating new cupboard() in main");
    new Cupboard();
    table.f2(1);
    cupboard.f3(1);
  }
  
  static Table table = new Table();
  static Cupboard cupboard = new Cupboard();
}

/*
output:

Bowl(1)
Bowl(2)
Table()
f1(1)
Bowl(4)
Bowl(5)
Bowl(3)
Cupboard()
f1(2)
Creating new cupboard() in main
Bowl(3)
Cupboard()
f1(2)
Creating new cupboard() in main
Bowl(3)
Cupboard()
f1(2)
f2(1)
f3(1)
 
*/
</span>

上面是一段程序，运行的结果，我也贴出来了，根据这个输出结果就可以看出JAVA中的初始化顺序：

主题思想就是：先静态对象而后非静态对象，静态对象只能初始化一次，类中的数据成员按顺序初始化。

1：

static Table table = new Table();

 Table对象初始化，进入到Table中，按顺序初始化两个静态Bowl

static Bowl bowl1 = new Bowl(1);//输出Bowl(1)
static Bowl bowl2 = new Bowl(2);//输出Bowl(2)

然后，Table（）本身构造函数初始化：

Table() {
    System.out.println("Table()");
    bowl2.f1(1);
  }
//输出Table()
//输出f1(1)

这里总共输出了：

Bowl(1)
Bowl(2)
Table()
f1(1)

2：

static Cupboard cupboard = new Cupboard();

Cupboard对象初始化，进入到Cupboard中，按顺序初始化两个静态Bowl

static Bowl bowl4 = new Bowl(4);//输出Bowl(4)
static Bowl bowl5 = new Bowl(5);//输出Bowl(5)

然后，数据成员初始化，即：

Bowl bowl3 = new Bowl(3);//输出Bowl(3)

接着,Cupboard()本身构造函数初始化：

public Cupboard() {
    System.out.println("Cupboard()");
    bowl4.f1(2);
  }
//输出Cupboard()
//输出f1(2)

这里总共输出了：

Bowl(4)
Bowl(5)
Bowl(3)
Cupboard()
f1(2)

3

进入到main函数，main也是static的方法，按顺序执行：

System.out.println("Creating new cupboard() in main");
//输出Creating new cupboard() in main

new Cupboard();

Cupboard对象初始化，进入到Cupboard中：

两个静态Bowl，已经初始化过，无需再次初始化；

然后，数据成员初始化，即：

Bowl bowl3 = new Bowl(3);//输出Bowl(3)

接着,Cupboard()本身构造函数初始化：

public Cupboard() {
    System.out.println("Cupboard()");
    bowl4.f1(2);
  }
//输出Cupboard()
//输出f1(2)

System.out.println("Creating new cupboard() in main");
//输出Creating new cupboard() in main

new Cupboard();

Cupboard对象初始化，进入到Cupboard中：

两个静态Bowl，已经初始化过，无需再次初始化；

然后，数据成员初始化，即：

Bowl bowl3 = new Bowl(3);//输出Bowl(3)

接着,Cupboard()本身构造函数初始化：

public Cupboard() {
    System.out.println("Cupboard()");
    bowl4.f1(2);
  }
//输出Cupboard()
//输出f1(2)

table.f2(1);
//调用table.f2(1);，输出f2(1)

cupboard.f3(1);
//调用cupboard.f3(1);，输出f3(1);

这里总共输出了：

Creating new cupboard() in main
Bowl(3)
Cupboard()
f1(2)
Creating new cupboard() in main
Bowl(3)
Cupboard()
f1(2)
f2(1)
f3(1)

所以结果，如上述output所述。