《Java从入门到精通》第十一章学习笔记

 1 public class Ex1 {
 2     
 3     private int num=10;
 4     public int getNum(){
 5         return this.num;
 6     }
 7     public void setNum(int num){
 8         this.num=num;
 9     }
10     public Ex1(){
11         try{
12             Class.forName("Ex123");   //尝试装载类
13         }catch(ClassNotFoundException e){  //捕获异常
14             e.printStackTrace();     //异常的输出方法
15         }
16         System.out.println("测试！");
17     }
18 
19     public static void main(String[] args) {
20         // TODO Auto-generated method stub
21         Ex1 test=new Ex1();
22         test.setNum(888);
23         System.out.println(test.getNum());
24     }
25 }

 1 public class Exc2 {
 2     int[] number={100,80,50,70,20,60};
 3     public void setNum(int index,int value){
 4         number[index]=value;
 5     }
 6     public int getNum(int index){
 7         return number[index];
 8     }
 9     public static void main(String[] args) {
10         Exc2 test=new Exc2();
11         for(int i=0;i<=10;i++){
12             try{
13                 System.out.println(test.getNum(i));
14                 System.out.println("第"+i+"个数组元素正常显示");
15             }catch(Exception e){
16                 e.printStackTrace();
17                 System.out.println("第"+i+"个元素无法读取！");
18                 break;
19             }
20         }
21     }
22 }

 1 /**
 2  * 编写一个异常类MyException，再编写一个Student类，其中有一个产生异常的speak(int m)方法
 3  * 当m大于1000时，方法抛出MyException对象
 4  * 通过主类测试
 5  * @author TS
 6  */
 7 public class Test{
 8     public class MyException extends Exception{
 9         public MyException(int i){
10             System.out.println("发生异常!i的值不能大于1000！");
11             System.out.println("目前i值为"+i);
12         }
13     }
14     public class Student{
15         public void speak(int m) throws MyException{
16             if(m>1000){
17                 throw new MyException(m);
18             }else{
19                 System.out.println("未发现异常！");
20             }
21         }
22     }
23     public static void main(String[] args){
24         Test test=new Test();
25         Student stu=test.new Student();
26         try{
27             stu.speak(1001);
28         }catch(MyException ex){
29             ex.printStackTrace();
30         }
31     }
32 }

 1 /**
 2  * 创建Number类，通过类的count()方法得到任意两个数相加的结果
 3  * 如果向count()方法传递负数，则抛出自定义异常
 4  * 在主类中测试
 5  * @author TS
 6  */
 7 public class Test {
 8     public class Number{
 9         long count(long m,long n) throws MyException{
10             if((m<0)||(n<0)){
11                 throw new MyException();
12             }else{
13                 System.out.println("正确返回！结果为"+(m+n));
14                 return m+n;
15             }
16         }
17     }
18     public class MyException extends Exception{
19         public MyException(){
20             System.out.println("此处抛出自定义异常MyException！");
21             System.out.println("提醒：加数中有负数！");
22         }
23     }
24     public static void main(String[] args){
25         Test test=new Test();
26         Number num=test.new Number();
27         try{
28             num.count(12, -15);
29         }catch(MyException e){
30             e.printStackTrace();
31         }
32         
33     }
34 
35 }