JAVA Chapter 6.pptVIP

5 Exception handling 程序: 从键盘上读取一个数字, 如果读取的不是一个数字, 请提示重新输入,并获取正确的数字. import java.io.*; public class readFile { public static void main(String arg[]) { byte[] b=new byte[34]; double i; while(true) { try{ System.in.read(b); i=Double.parseDouble((new String(b).trim())); System.out.println(the digital is :+i); break; }catch(IOException e) { System.out.println(io error); break; } catch(NumberFormatException e1) { System.out.println(input a right digital......); } } }} 5.1 catch exceptions The process of catching exceptions throw exceptions(抛出异常) catch exceptions (捕捉异常) try{　　......1 … ..2 }catch( ExceptionName1 e ) {　　　......　　} catch( ExceptionName2 e ) {　　 ...... } finally {……………} public class ExceptionExam1 { static int a, c; public static void main(String[] args) { try { c=100/Integer.parseInt(args[0].trim()); System.out.println( the result is :+c); System.exit(0); } catch(ArithmeticException e) { a= -1; System.out.println(/ by zero); } catch (Exception e2) { a= -1 ; System.out.println(the reason of exception is :+ e2.getMessage());} finally { if(a== -1) System.out.println(程序执行发生异常！); else System.out.println(程序正常执行完毕!); } } } 5.2 Types of Exceptions public Exception() public Exception(String s): 该参数一般表示该异常对应的错误的描述。? public String toString(): 返回描述当前异常对象信息的字符串。 public String getMessage(): 返回描述当前异常对象信息的详细信息。 public void printStackTrace(): 打印当前异常对象使用栈的轨迹。 5.3 Create your own Exceptions Define your own exception Just extending Throwable or Exception -----just modify the constructor. Throw your exception throw new aException(“a exception”); example a/b and both a and b are not zero . public class ExceptionExam2 { static double a,b,c; public static void main(String[] args)