static 修飾成員變數：

 1 package cn.itcast.day08.demo03;
 2 
 3 public class Student {
 4 
 5     private int id; //學號
 6     private String name;
 7     private int age;
 8     static String room; //所在教室
 9     private static int idCounter = 0; //學號計數器，每當new了一個新物件的時候，計數器++
10 
11     public Student() {
12         this
 
.id = ++idCounter;
13     }
14 
15     public Student(String name, int age) {
16         this.name = name;
17         this.age = age;
18         this.id = ++idCounter;
19     }
20 
21     public String getName() {
22         return name;
23     }
24 
25     public void setName(String name) {
26         this
 
.name = name;
27     }
28 
29     public int getAge() {
30         return age;
31     }
32 
33     public void setAge(int age) {
34         this.age = age;
35     }
36 
37     public int getId() {
38         return id;
39     }
40 
41     public void setId(int id) {
42         this.id = id;
43     }
44
 
 }

 1 /*
 2 如果一個成員變數使用了 static 關鍵字，那麼這個變數不再屬於物件自己，而是屬於所在的類。 多個物件共享同一份資料
 3  */
 4 
 5 public class Demo01StaticField {
 6 
 7     public static void main(String[] args) {
 8         Student one = new Student("郭靖", 19);
 9         one.room = "101Room";
10         System.out.println("name: " + one.getName()
11                 + ",age: " + one.getAge() + ",room: " + one.room + ",id: " + one.getId());
12 
13         Student two = new Student("黃蓉", 16);
14         System.out.println("name: " + two.getName()
15                 + ".age: " + two.getAge() + ",room: " + two.room + ",id: " + two.getId());
16 
17     }
18 }