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一、读取文件的步骤：
读取文件操作的每一步都依赖上一步的实现
二、代码分析
1、传统型错误码反馈机制
class errorCodeTypeFile{
int errorCode = 0;
if(theFileOpened) {
determine its size;
if(gotTheFileLength ){
allocate that much memory;
if(gotEnoughMemory){
read the file into the memory;
if(readFailed){
errorCode = -1;
}
}
else {
errorCode = -2;
}
}
else {
errorCode = -3;
}
close the file;
if(theFileDidn‘tClose && errorCode == 0){
errorCode = -4;
}
else {
errorCode = errorCode and -4;
}
}
else {
errorCode = -5;
}
return errorCode;
}
通过反馈的错误码，我们可以了解到哪一步发生错误，但是该种代码可读性差，难以修改，逻辑不清晰。
2、添加异常捕捉机制后的代码
try {
open the file;
determine its size;
allocate that much memory;
read the file into the memory;
close the file;
} catch (fileOpenFailed ){
do something;
} catch (sizeDeterminedFaile){
do something;
} catch (memeoryAllocationFailed){
do something;
} catch (readFailed){
do something;
} catch (fileClosedFailed){
do something;
}
代码添加异常捕捉机制后，通过catch后的语句可以了解到异常种类，而且该代码具有可读性高，逻辑分明，通常把try后语句称为业务逻辑代码，catch后语句称为异常处理代码。
三、今日总结
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原文地址：http://www.cnblogs.com/benbenji/p/5636109.html
