异常练习（自定义异常）

练习一：

 1 package Exception;
 2 /**
 3  * 计算一个圆和长方形的面积？
 4  * 注意：面积不能为0和负数。请用异常来描述；
 5  * @author asus1
 6  *
 7  */
 8 //自定义一个异常
 9 class NovalueException extends RuntimeException{
10     NovalueException(String mssage){
11         super(mssage);
12     }
13 }
14 public class ExceptionDemo3 {
15 
16     public static void main(String[] args) {
17         try {
18             ricImpl ri = new ricImpl(5,2);
19             double riArea = ri.getArea();
20             System.out.println(riArea);
21             
22             CirlcImpl ci = new CirlcImpl(-5);
23             double ciArea = ci.getArea();
24             System.out.println(ciArea);
25             
26         } catch (NovalueException e) {
27             System.out.println(e.toString());
28         }
29         
30     }
31 
32 }
33 
34 interface Shape {
35     double getArea();
36 }
37 
38 class ricImpl implements Shape{
39     private double width;
40     private double height;
41     ricImpl(double width,double height) throws NovalueException{
42         if(width <=0 || height<=0){
43             throw new NovalueException("非法数据");
44         };
45         this.width = width;
46         this.height = height;
47     }
48     public double getArea(){
49         return width*height;
50     }
51 }
52 class CirlcImpl implements Shape{
53     private double radius;
54     public static final double PI = 3.14;
55     CirlcImpl(double radius) throws NovalueException{
56         if(radius <=0){
57             throw new NovalueException("圆--非法数据");
58         }
59         this.radius = radius;
60     }
61     public double getArea(){
62         return radius*radius*PI;
63     }
64 }

练习二：

 1 package Exception;
 2 /**
 3  * 老师讲课
 4  * 问题：1.电脑蓝屏了
 5  *         2.电脑冒烟了
 6  * 需求：解决以上两异常
 7  * @author asus1
 8  *
 9  */
10 class lanpinException extends Exception{  //蓝屏异常
11     lanpinException(String mssage){
12         super(mssage);
13     }
14 }
15 class maoyanException extends Exception{  //冒烟异常
16     maoyanException(String mssage2){
17         super(mssage2);
18     }
19 }
20 public class Exception_lianxi {
21 
22     public static void main(String[] args) {
23         Teacher t = new Teacher("童");
24         t.prelect();
25         System.out.println("讲课了");
26     }
27 
28 }
29 class Teacher{
30     private String name;
31     public Teacher(String name) {
32         super();
33         this.name = name;
34     }
35     public void prelect(){
36         Complate co = new Complate();
37         try {//正常
38             co.run();
39         } catch (lanpinException e) {  //蓝屏异常抛出
40             //解决蓝屏异常的代码
41             System.out.println(e.getMessage());
42             co.reset();                
43         }catch (maoyanException e) {  //冒烟异常抛出
44             //解决冒烟异常的代码
45             System.out.println(e.getMessage());
46             gotolianxi lianxi = new gotolianxi();
47             //lianxi.toString();
48         }
49         
50     }
51 }
52 class gotolianxi{
53     public gotolianxi(){
54         System.out.println("去练习");
55     }
56 }
57 class Complate{
58     private int state = 3;  //1- 正常 ; 2- 蓝屏;  3- 冒烟;
59     
60     public void run() throws lanpinException,maoyanException{
61         if(state == 1){
62             System.out.println("runing!!");
63         }
64         if(state == 2){
65             throw new lanpinException("电脑蓝屏了-");//抛出编译时检测的异常 需要在方法外声明定义这个异常
66         }
67         if(state == 3){
68             throw new maoyanException("电脑冒烟了-");
69         }
70     }
71     public void reset(){
72         System.out.println("电脑重启ing");
73     }
74 }