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Android Android Data Persistence Introduction to Data Persistence Handling an Exception

yossi nagar
yossi nagar
2,652 Points
Posted by yossi nagar
yossi nagar
2,652 Points

pls explain me try and catch

Handling an Exception

CodeChallenge.java 
// assetManager, assetName, and fileToWrite have been initialized elsewhere
try {
InputStream in = assetManager.open(assetName);
FileOutputStream out = new FileOutputStream(fileToWrite);
copyFile(in, out);
}catch(Exception e) {

1 Answer

Steve Hunter
Steve Hunter
57,712 Points

Hi Yossi,

You're prety much there with your code - there's only one last bit to finish off.

Inside the try block, you put the code that you know can throw exceptions. Often this is file IO operations, code requiring network access etc. Things where external factors can cause it not to function as you intend. So, the code is tried - if it work, cool - away your app goes working as you want it to. If it fails, though, you then catch the exception. There are different sorts of exceptions, in this challenge, we're dealing with a basic catch-all Exception which is the general superclass, I guess.

Inside the catch, you can manage the exception. There's lots of ways to do this - it could be utilising default settings to bypass the requirements of the code that failed, or it could just be logging the problem, as in this example. The exception is used as a parameter, passed into the catch block as an instance of its Exception type.

Here we just want to use printStackTrace() to output the issue:

try {
  InputStream in = assetManager.open(assetName);
  FileOutputStream out = new FileOutputStream(fileToWrite);
  copyFile(in, out);
} catch (Exception e){
  e.printStackTrace();  
}

I hope that helps.

Steve.