JAVA例9.5-9.7及实验44-49.docx

例9.5 /filename App9_5.java 使用throws语句在方法中抛出异常public class App9_5static void check(String str1)throws NullPointerException /方法头抛出空指针异常if(str1.length()2) /如果字符串参数str的字符长度大于2str1=null; /则字符串参数赋值为空System.out.println(str1.length(); /试图输出空串的长度会抛出空指针异常char ch;for(int i=0;i60)System.out.println(成绩为：+num+ 及格);elseSystem.out.println(成绩为：+num+ 不及格);catch(NullPointerException e)System.out.println(空指针异常：+e.toString();catch(NumberFormatException ex)System.out.println(输入的参数不是数值类型);catch(Exception e)System.out.println(命令行中没有提供参数);例9.6/filename App9_6.java 利用IOException的异常处理import java.io.*; /加载java.io类库中的所有类public class App9_6public static void main(String args) throws IOExceptionString str;BufferedReader buf;buf=new BufferedReader(new InputStreamReader(System.in);while(true)trySystem.out.print(输入字符串：);str=buf.readLine(); /将从键盘输入的数据赋给变量strif(str.length()0) break;elsethrow new IOException(); /抛出输入输出异常catch(IOException e)System.out.println(必须输入字符串!);continue;String s=str.toUpperCase(); /将str中的内容转换成大写，赋给变量sSystem.out.println(转换后的字符串为：+s);例9.7/filename App9_7.java 自定义异常类的用法class CircleException extends Exception /自定义异常类double radius;CircleException(double r) /自定义异常类的构造方法radius=r;public String toString()return 半径r=+radius+不是一个正数;class Circle /定义Circle类private double radius;public void setRadius(double r) throws CircleExceptionif(r0) throw new CircleException(r); /抛出异常elseradius=r;public void show()System.out.println(圆面积=+3.14*radius*radius);public class App9_7 /定义主类public static void main(String args)Circle cir=new Circle();trycir.setRadius(-2.0); /捕获由setRadius()方法抛出的异常catch(CircleException e)System.out.println(自定义异常：+e.toString()+);cir.show();实验44 java的异常处理机制。/DivideZero.javapublic class DivideZeropublic static void main(String args)int x=0; int y=0; y=3/x; System.out.println(程序结束); 实验45 常见的异常/OtherException.javapublic class OtherExceptionpublic static void main(String args)tryint a=null;a0=1;catch(NullPointerException e)System.out.println(空指针异常);tryString str=null;str.length();catch(NullPointerException e)System.out.println(空指针异常);tryObject obj=new Object();String str=(String)obj;catch(ClassCastException e)System.out.println(类型强制转换异常);tryint a=new int-1;catch(NegativeArraySizeException e)System.out.println(数组负下标异常);tryint a=new int1;a0=0;a1=1;catch(ArrayIndexOutOfBoundsException e)System.out.println(数组下标越界异常);实验46 多异常处理。/ManyException.javapublic class ManyExceptionpublic static void main(String args)int i;int a=1,2,3,4;for(i=0;i0) throw new AaaException(); else throw new BbbException();catch(AaaException e)System.out.println(执行aaa异常处理程序);catch(BbbException e)System.out.println(执行bbb异常处理程序);实验49 必须要捕获的异常/CatchException.javaimport java.io.*;public class CatchExceptionpublic static void main(String args)System.out.println(程序开始);trySystem.in.read();catch(Exception e)System.out.println(程序结束);将try及catch删去后/CatchException.ja