C++第18章 异常处理PPT学习课件

异常处理,主讲教师：陈婷,18.1异常的概念18.2异常的实现18.3异常的规则18.4默认异常处理18.5异常派生族系,本章内容,#includeusingnamespacestd;voiddivided(doublea,doubleb)/实现两个浮点数除法doubleresult=a/b;/会不会有问题？coutab;divided(a,b);/调用divided函数return0;,18.1异常的概念,Ch18_01,#include#includeusingnamespacestd;intmain()char*ch;/字符指针longlongsize;coutsize;coutch;cout“StringSize=”strlen(ch)b;divided(a,b);return0;,18.2异常的实现,Ch18_03,说明：try语句块表示块中的语句可能会发生异常，放在其中加以监控。注意：C+只理会受监控的运行异常。throw后面的表达式的类型被称为所引发的异常类型。在try语句块之后必须紧跟一个或多个catch语句，目的是对发生的异常进行处理（注意：try之前不允许出现catch）。catch()括号中的声明只能容纳一个形参，当类型与抛掷异常的类型匹配时，该catch()语句块便称捕获了一个异常而转到其块中进行异常处理。catch()形参的值则为throw语句抛掷的异常值。当异常发生时，try语句块中异常之后的语句不再执行。,18.2异常的实现,#includeusingnamespacestd;voiddivided(doublea,doubleb)/实现两个浮点数除法doubleresult;try/定义异常if(b=0.0)throwb;/抛掷异常result=a/b;coutab;divided(a,b);return0;,18.3异常的规则,Ch18_04,C+只理会受监控的运行异常,#includeusingnamespacestd;intmain()intidx;coutidx;try/定义异常if(idx=0)throw10;/int型异常elseif(idx=1)throw13.14;/double型异常elseif(idx=2)throwc;/char型异常elsethrow“C+”;/字符串异常,18.3异常的规则,catch(intn)/捕获int型异常cout“IntException:”nendl;catch(doubled)/捕获double型异常cout“DoubleException:”dendl;catch(charc)/捕获char型异常cout“CharException:”cendl;catch(char*s)/捕获字符串异常cout“StringException:”sidx;try/定义异常if(idx=0)throw10;/int型异常elseif(idx=1)throw13.14;/double型异常elseif(idx=2)throwc;/char型异常elsethrow“C+”;/字符串异常,18.3异常的规则,catch(int)/捕获int型异常cout“IntException!”endl;catch(double)/捕获double型异常cout“DoubleException!”endl;catch(char)/捕获char型异常cout“CharException!”endl;catch(char*)/捕获字符串异常cout“StringException!”idx;try/定义异常if(idx=0)throw10;/int型异常elseif(idx=1)throw13.14;/double型异常elseif(idx=2)throwc;/char型异常elseif(idx=3)throwCException();/类异常,18.3异常的规则,elsethrow“C+”;/字符串异常catch(int)/捕获int型异常cout“IntException!”endl;catch(double)/捕获double型异常cout“DoubleException!”endl;catch(char)/捕获char型异常cout“CharException!”endl;catch(CException)/捕获类异常cout“ClassException!”idx;try/定义异常if(idx=0)throw10u;/unsignedint型异常elseif(idx=1)throw13.14f;/float型异常elseif(idx=2)throwc;/char型异常elsethrowCException();/类异常,18.3异常的规则,catch(int)/捕获int型异常cout“IntException!”endl;catch(double)/捕获double型异常cout“DoubleException!”endl;catch(char)/捕获char型异常cout“CharException!”endl;catch(CException)/捕获类异常cout“ClassException!”b;try/定义异常if(b=0.0)throwb;/抛掷异常result=a/b;catch(double)/捕获、处理异常coutb;result=a/b;catch(int)cout“IntException!”endl;/捕获、处理异常cout“a/b=”resultendl;/catch块后的语句return0;,18.3异常的规则,Ch18_08,当catch分程序执行完毕时，则跟随最后一个catch分程序的代码就会被执行。,#includeusingnamespacestd;doubledivided(doublea,doubleb)/实现两个浮点数除法if(b=0.0)throwb;/抛出异常returna/b;intmain()try/定义异常cout“13.14/2.0=”divided(13.14,2.0)endl;cout“13.14/0.0=”divided(13.14,0.0)endl;cout“13.14/3.0=”divided(13.14,3.0)endl;catch(double)/捕获异常cout“Exceptionofdividingzerooccurs!”idx;try/定义异常if(idx=0)throw10;/int型异常elseif(idx=1)throw13.14;/double型异常elseif(idx=2)throwc;/char型异常elseif(idx=3)throwCException();/类异常elsethrow“Exception”;/字符串异常,18.4默认异常处理,catch(int)/捕获int型异常cout“IntException!”endl;catch(double)/捕获double型异常cout“DoubleException!”endl;catch(char)/捕获char型异常cout“CharException!”endl;catch(CException)/捕获类异常cout“ClassException!”endl;catch()/捕获所有其他异常cout“UnexpectedException!”exception;try/定义异常switch(exception)case1:throwIncorrectDirectory();break;/抛掷派生类异常case2:throwIncorrectFormat();break;/抛掷派生类异常case3:throwFileCorruption();break;/抛掷派生类异常case4:throwFileError();break;/抛掷基类异常default:throw“Unexpected”;break;/抛掷字符串异常,18.5异常派生族系,catch(FileError)/捕获基类异常cout“FileErrorException!”endl;catch(IncorrectDirectory)/捕获派生类异常cout“IncorrectDirectoryException!”endl;catch(IncorrectFormat)/捕获派生类异常cout“IncorrectFormatException!”endl;catch(FileCorruption)/捕获派生类异常cout“FileCorruptionException!”endl;catch()/捕获其他异常cout“UnexpectedException!”exception;tryswitch(exception)case1:throwIncorrectDirectory();break;/抛掷派生类异常case2:throwIncorrectFormat();break;/抛掷派生类异常case3:throwFileCorruption();break;/抛掷派生类异常case4:throwFileError();break;/抛掷基类异常default:throw“Unexpected”;break;/抛掷字符串异常,18.5异常派生族系,正确异常处理方式,catch(IncorrectDirectory)/捕获派生类异常cout“IncorrectDirectoryException!”endl;catch(IncorrectFormat)/捕获派生类异常cout“IncorrectFormatException!”endl;catch(FileCorruption)/捕获派生类异常cout“FileCorruptionException!”endl;catch(FileError)/捕获基类异常cout“FileErrorException!”endl;catch()/捕获其他异常cout“UnexpectedException!”endl;return0;,18.5异常派生族系,将catch(基类)语句块总是放在catch(派生类)语句块的后面！,下列关于异常的叙述错误的是：A.编译错属于异常，可以抛出B.运行错属于异常C.硬件故障也可当异常抛出D.只要是编程者认为是异常的都可当异常抛出,下列叙述错误的是：throw的操作数表示异常类型B.throw的操作数值可以区别不同的异常C.throw抛出不同异常时需要用不同的操作数类型来区分D.throw语句抛出的异常可以不被捕获,下列叙述错误的是