Java静态方法和静态属性

动手动脑①

 1 package test_1;
 2 
 3 public class Test {
 4 
 5     public static void main(String[] args) {
 6         // TODO 自动生成的方法存根
 7         Foo obj1=new Foo();
 8         Foo obj2=new Foo();
 9         System.out.println(obj1==obj2);
10     }
11 }
12 class Foo{
13     int value=100;
14 }

动手动脑②：类字段的初始化顺序：

 1 package test_1;
 2 
 3 public class Test {
 4 
 5     public static void main(String[] args) {
 6         // TODO 自动生成的方法存根
 7         InitializeBlockClass obj=new InitializeBlockClass();
 8         System.out.println(obj.getField());
 9         
10         obj=new InitializeBlockClass(300);
11         System.out.println(obj.getField());
12     }
13 }
14     class InitializeBlockClass{
15         
16         {
17             setField(200);        //代码块定义值是200
18         }
19         private int field=100;    //定义初始值是 100
20         InitializeBlockClass(int value) {   //传入参数是300
21             this.setField(value);
22         }
23          InitializeBlockClass() {
24         }
25         public int getField() {
26             return field;
27         }
28         public void setField(int field) {
29             this.field = field;
30         }
31     }

 1 package test_1;
 2 
 3 public class Test {
 4 
 5     public static void main(String[] args) {
 6         // TODO 自动生成的方法存根
 7         InitializeBlockClass obj=new InitializeBlockClass();
 8         System.out.println(obj.getField());
 9         
10         obj=new InitializeBlockClass(300);
11         System.out.println(obj.getField());
12     }
13 }
14     class InitializeBlockClass{

15         private int field=100;    //定义初始值是 100
16         {
17             setField(200);        //代码块定义值是200
18         }
19         
20         InitializeBlockClass(int value) {   //传入参数是300
21             this.setField(value);
22         }
23          InitializeBlockClass() {
24         }
25         public int getField() {
26             return field;
27         }
28         public void setField(int field) {
29             this.field = field;
30         }
31     }

 1 package test_1;
 2 
 3 class Root
 4 {
 5     static
 6     {
 7         System.out.println("Root的静态初始化块");
 8     }
 9     
10     {
11         System.out.println("Root的普通初始化块");
12     }
13     
14     public Root()
15     {
16         System.out.println("Root的无参数的构造器");
17     }
18 }
19 class Mid extends Root
20 {
21     static
22     {
23         System.out.println("Mid的静态初始化块");
24     }
25     {
26         System.out.println("Mid的普通初始化块");
27     }
28     public Mid()
29     {
30         System.out.println("Mid的无参数的构造器");
31     }
32     public Mid(String msg)
33     {
34         //通过this调用同一类中重载的构造器
35         this();
36         System.out.println("Mid的带参数构造器，其参数值：" + msg);
37     }
38 }
39 class Leaf extends Mid
40 {
41     static
42     {
43         System.out.println("Leaf的静态初始化块");
44     }
45     {
46         System.out.println("Leaf的普通初始化块");
47     }    
48     public Leaf()
49     {
50         //通过super调用父类中有一个字符串参数的构造器
51         super("Java初始化顺序演示");
52         System.out.println("执行Leaf的构造器");
53     }
54 
55 }
56 
57 public class TestStaticInitializeBlock
58 {
59     public static void main(String[] args) 
60     {
61         new Leaf();
62         
63 
64     }
65 }

规律总结：

一个父类后继承两个子类，调用顺序为：总顺序先static代码块后普通代码块最后构造代码块，先父类后子类，先无参构造，后带参构造！

*****************************************************

动手动脑④：

 1 package test_1;
 2 
 3 public class StaticStudy {
 4     static int staticnum=1;
 5     private int num;
 6     public static void display() {
 7         StaticStudy test=new StaticStudy();
 8         System.out.println("在静态方法中输出静态变量："+test.staticnum);
 9         System.out.println("在静态方法中输出非静态变量："+test.num);
10     }
11     public int getNum() {
12         return num;
13     }
14     public void setNum(int num) {
15         this.num = num;
16     }
17     public StaticStudy(int num) {
18         this.num = num;
19     }
20     public StaticStudy() {
21         
22     }
23     public static void main(String[] args) {
24         // TODO 自动生成的方法存根
25         StaticStudy test0=new StaticStudy(100);
26         test0.display();
27     }
28 
29 }


//只需要在静态变量里实例化一个本类的对象，通过这个对象取用本对象的数据成员！

动手动脑⑤：

Java中的包装类

 1 package test_1;
 2 
 3 public class StrangeIntegerBehavior 
 4 {
 5     public static void main(String[] args)
 6     {
 7         Integer i1=100;
 8        
 9         Integer j1=100;
10         
11         System.out.println(i1==j1);
12 
13         Integer i2=129;
14         
15         Integer j2=129;
16         
17         System.out.println(i2==j2);
18     
19     }
20 }