需要捕获IOExceptions&例外 [英] The need to catch IOExceptions & Exceptions

问题描述

如果使用扫描器对象在txt文件中读取的程序只产生FileNotFoundException，那么应该总是捕获IOException / Exception？

这些额外的代码是不需要的还是重要的？

  import java .io.File; 
 import java.io.FileNotFoundException; 
 import java.util.Scanner; 
 
 
 public class TestingScanner {
 public TestingScanner（）{
 readFile（dummy.txt）; 
} 
 
 public void readFile（String filePath）{
文件文件=新建文件（filePath）; 
扫描仪扫描仪= null; 
 
 try {
 scanner = new Scanner（file）; 
 
 while（scanner.hasNext（））{
 String line = scanner.nextLine（）; 
 if（line.matches（^。+ @ yahoo\\\.com？（\\\.uk）？$））
 System.out.println（line）; 
} 
} catch（FileNotFoundException e）{
 System.out.println（错误：无法加载到+ filePath中）; 
 e.printStackTrace（）; 
} finally {
 if（scanner！= null）
 scanner.close（）; 
} 
} 
} 
  

解决方案

我的经验法则是广泛地捕捉异常（捕获异常或Throwable），除非有特定的东西，我会为特定的异常做不同的。

例如，如果一个方法抛出两个不同的异常，我将处理这两个异常，然后我将捕获异常。但是，如果我正在处理它们不同，那么我会单独捕获每个并且相应地处理它们。

这种方法中的扳手是运行时异常。一个想法是让RuntimeExceptions冒泡起来。但是我发现，在我遇到异常的情况下，我想要所有的...，有时甚至是Throwables（只有通过捕捉异常而不是Throwable才被烧掉）。

这里有一些例子：

  public void myMethod（）throws IOException，FileNotFoundException（）; 
  

在我不想让异常冒泡的情况下（需要处理它们） p>

  try {
 myMethod（）; 
 catch（异常e）{
 //处理
} 
  

在我遇到异常的情况下，需要为FileNotFound做不同的事情。

  try {
 myMethod ）; 
 catch（FileNotFoundException fe）{
 //处理文件未找到
} 
 catch（异常e）{
 //处理
} 
  

在我正在让异常起泡的情况下，因为我进一步了解了链条，一些非常酷的异常处理代码是处理它，我想避免多次记录异常：

  myMethod（）; 
  

在我正在让异常起泡的情况下，除了FileNotFound。

  try {
 myMethod（）; 
 catch（FileNotFoundException fe）{
 //未找到句柄文件
} 
  

Should one always catch an IOException/Exception if a program reading in a txt file using a scanner object produces nothing but a FileNotFoundException?

Would such extra code be unneeded or important?

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;


public class TestingScanner {
    public TestingScanner() {
        readFile("dummy.txt");
    }

    public void readFile(String filePath) {
        File file = new File(filePath);
        Scanner scanner = null;

        try {
            scanner = new Scanner(file);

            while (scanner.hasNext()) {
                String line = scanner.nextLine();
                if (line.matches("^.+@yahoo\\.com?(\\.uk)?$"))
                    System.out.println(line);
            }
        } catch (FileNotFoundException e) {
            System.out.println("ERROR: Couldn't Load in " + filePath);
            e.printStackTrace();
        } finally {
            if (scanner != null)
                scanner.close();
        }
    }
}

解决方案

My rule of thumb is to go broad with exception catching (catching Exception or Throwable) unless there is something specific I will want do different for a specific exception.

For example, if a method throws two different Exceptions, and I will be handling both the same then I will just catch Exception. But if I am handling them different then I would catch each individually and process them accordingly.

The wrench in this approach is "what about RuntimeExceptions". One school of thought is to allow RuntimeExceptions to bubble up. But what I find is that in situations where I am catching exceptions, then I want all of them... and sometimes even Throwables (I got burnt once by only catching Exception and not Throwable).

Here are some examples:

public void myMethod() throws IOException, FileNotFoundException ();

In situation where I want to not let Exceptions bubble up (need to deal with them all)

try{
   myMethod();
catch(Exception e) {
//handle it
}

In situation where I am catching Exceptions and need to do something different for FileNotFound.

try{
   myMethod();
catch(FileNotFoundException  fe){
    //handle file not found
}
catch(Exception e) {
    //handle it
}

In situation where I am letting Exceptions bubble up because I know further up the chain some really cool exception handling code is handling it and I want to avoid logging the exception multiple times:

myMethod();

In situation where I am letting Exceptions bubble up except for FileNotFound.

try{
   myMethod();
catch(FileNotFoundException  fe){
    //handle file not found
}

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