Using try/catch for preventing app from crashes

Of course, there are always exceptions to rules, but if you need a rule of thumb - then you are correct; empty catch blocks are "absolutely" bad practice.

Let's have a closer look, first starting with your specific example:

try {
View view = findViewById(R.id.toolbar);
}
catch(Exception e) { }

So, a reference to something is created; and when that fails ... it doesn't matter; because that reference isn't used in the first place! The above code is absolutely useless line noise. Or does the person who wrote that code initially assume that a second, similar call would magically no longer throw an exception?!

Maybe this was meant to look like:

try {
View view = findViewById(R.id.toolbar);
... and now do something with that view variable ...
}
catch(Exception e) { }

But again, what does this help?! Exceptions exist to communicate respectively propagate error situations within your code. Ignoring errors is rarely a good idea. Actually, an exception can be treated in ways like:

• You give feedback to the user; (like: "the value you entered is not a string, try again"); or to engage in more complex error handling
• Maybe the problem is somehow expected and can be mitigated (for example by giving a "default" answer when some "remote search" failed)
• ...

Long story short: the minimum thing that you do with an exception is to log/trace it; so that when you come in later debugging some problem you understand "OK, at this point in time that exception happened".

And as others have pointed out: you also avoid catching for Exception in general (well, depending on the layer: there might be good reasons to have some catch for Exception, and even some kinds of Errors at the highest level, to make sure that nothing gets lost; ever).

Finally, let's quote Ward Cunningham:

You know you are working with clean code when each routine you read turns out to be pretty much what you expected. You can call it beautiful code when the code also makes it look like the language was made for the problem.

Let that sink in and meditate about it. Clean code does not surprise you. The example you are showing to us surprises everybody looking at.

Update, regarding the update that the OP asks about

try {
do something
}
catch(Exception e) {
print stacktrace
}

Same answer: doing that "all over the place" is also bad practice. Because this code is also surprising the reader.

The above:

• Prints error information somewhere. It is not at all guaranteed that this "somewhere" resembles a reasonable destination. To the contrary. Example: within the application I am working with, such calls would magically appear in our trace buffers. Depending on context, our application might pump tons and tons of data into those buffers sometimes; making those buffer prune every few seconds. So "just printing errors" often translates to: "simply loosing all such error information".
• Then: you don't do try/catch because you can. You do it because you understand what your code is doing; and you know: I better have a try/catch here to do the right thing (see the first parts of my answer again).

So, using try/catch as "pattern" like you are showing; is as said: still not a good idea. And yes, it prevents crashes; but leads to all kind of "undefined" behavior. You know, when you just catch an exception instead of properly dealing with it; you open a can of worms; because you might run into myriads of follow-on errors that you later don't understand. Because you consumed the "root cause" event earlier on; printed it somewhere; and that somewhere is now gone.

It's definitely a bad programming practice.

From the current scenario, if there are hundreds of try catch like this, then you won't even know where the exception occurs without debugging the application, which is a nightmare if your application is in production environment.

But you can include a logger so that you get to know when an exception is throws (and why). It won't change your normal workflow.

...
try {
View view = findViewById(R.id.toolbar);
}catch(Exception e){
logger.log(Level.SEVERE, "an exception was thrown", e);
}
...

I have been developing android apps for the past 4-5 years and never used a try catch for view initialisation.

If its a toolbar do like this

Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);

eg:- To get a TextView from a view(fragment/dialog/any custom view)

TextView textview = (TextView) view.findViewById(R.id.viewId);

TextView textview = (TextView) view.findViewById(R.id.viewId);

instead of this

View view = findViewById(R.id.toolbar);

A view object has minimum reach compared to its real view type.

Note:- May be it crashed because the view was loaded. But adding try catch is a bad practice.

Yes, try/catch is used to prevent app from crashing but You certainly don't need try/catch for fetching a view from XML as depicted in your question.

try/catch is generally used while making any http request, while parsing any String to URL, creating URL connections, etc. and also make sure to print stack trace. Not printing it doesn't make much sense in surrounding it with try/catch.

From the Android documentation:

Let's entitle it as -

Don't Catch Generic Exception

It can also be tempting to be lazy when catching exceptions and do something like this:

try {
someComplicatedIOFunction();        // may throw IOException
someComplicatedParsingFunction();   // may throw ParsingException
someComplicatedSecurityFunction();  // may throw SecurityException
// phew, made it all the way
} catch (Exception e) {                 // I'll just catch all exceptions
handleError();                      // with one generic handler!
}

In almost all cases it is inappropriate to catch generic Exception or Throwable (preferably not Throwable because it includes Error exceptions). It is very dangerous because it means that Exceptions you never expected (including RuntimeExceptions like ClassCastException) get caught in application-level error handling.

It obscures the failure handling properties of your code, meaning if someone adds a new type of Exception in the code you're calling, the compiler won't help you realize you need to handle the error differently.

Alternatives to catching generic Exception:

• Catch each exception separately as separate catch blocks after a single try. This can be awkward but is still preferable to catching all Exceptions.
  Edit by author: This one is my choice. Beware repeating too much code in the catch blocks. If you are using Java 7 or above, use multi-catch to avoid repeating the same catch block.
• Refactor your code to have more fine-grained error handling, with multiple try blocks. Split up the IO from the parsing, handle errors separately in each case.
• Re-throw the exception. Many times you don't need to catch the exception at this level anyway, just let the method throw it.

In most cases you shouldn't be handling different types of exception the same way.

^{Formatting / paragraphing slightly modified from the source for this answer.}

P.S. Don't be afraid of Exceptions!! They are friends!!!

We pretty use much your same logic. Use try-catch to prevent production apps from crashing.

Exceptions should be NEVER ignored. It is a bad coding practice. The guys maintaining the code will have a really hard time localizing the part of code that raised the exception if they are not logged.

We use Crashlytics to log the exceptions. The code will not crash (but some functionality will be disrupted). But you get the exception log in the dashboard of Fabric/Crashlytics. You can look at these logs and fix the exceptions.

try {
codeThatCouldRaiseError();
} catch (Exception e) {
e.printStackTrace();
Crashlytics.logException(e);
}

It's bad practice to use catch(Exception e){} because you're essentially ignoring the error. What you probably want to do is something more like:

try {
//run code that could crash here
} catch (Exception e) {
System.out.println(e.getMessage());
}

I would put this as a comment to some other answer, but I don't have the reputation for that yet.

You are correct in saying that it's bad practice, in fact what you posted shows different types of bad practice in regards to exceptions.

1. Lack of error handling
2. Generic Catch
3. No intentional exceptions
4. Blanket Try/catch

I'll try to explain all of those via this example.

try {
User user = loadUserFromWeb();
if(user.getCountry().equals("us")) {
enableExtraFields();
}
fillFields(user);
} catch (Exception e) {
}

This can fail in several ways that should be handled differently.

1. The fields will not be filled, so the user is presented with an empty screen and then... what? Nothing - lack of error handling.
2. There's no distinction between different types of errors, e.g. Internet problems or problems with the server itself (outage, broken request, corrupted transmission, ...) - Generic catch.
3. You can not use exceptions for your own purposes because the current system interferes with that. - No intentional exceptions
4. Unessential and unexpected errors (e.g. null.equals(...)) can cause essential code not to execute. - Blanket try/catch

Solutions

(1) First of all, failing silently is not a good thing. If there's a failure, the app won't work. Instead there should be an attempt to resolve the problem or a display a warning, for example "Could not load user data, maybe you're not connected to the Internet?". If the app is not doing what it's supposed to, that's way more frustrating for a user than if it just closes itself.

(4) If the User is incomplete, e.g. the country is not known and returns null. The equals method will create a NullPointerException. If that NPE is just thrown and caught like above, the fillFields(user) method will not be called, even though it could still be executed without problems. You could prevent this by including null checks, changing execution order, or adjusting the try/catch scope. (Or you could do save coding like this: "us".equals(user.getCountry()), but I had to provide an example). Of course any other exception will also prevent fillFields() from being executed, but if there's no user, you probably don't want it executed anyway.

(1, 2, 3)Loading from web often throws a variety of exceptions, from IOException to HttpMessageNotReadable exception to even just returning. Could be that the user isn't connected to the internet, could be that there was a change to a backend server or it is down, but you don't know because you do catch(Exception) - instead you should catch specific exceptions. You can even catch several of them like this

try{
User user = loadUserFromWeb(); //throws NoInternetException, ServerNotAvailableException or returns null if user does not exist
if(user == null) {
throw new UserDoesNotExistException(); //there might be better options to solve this, but it highlights how exceptions can be used.
}
fillFields(user);
if("us".equals(user.getCountry()) {
enableExtraFields();
}
} catch(NoInternetException e){
displayWarning("Your internet conneciton is down :(");
} catch(ServerNotAvailableException e){
displayWarning("Seems like our server is having trouble, try again later.");
} catch(UserDoesNotExistException e){
startCreateUserActivity();
}

I hope that explains it.

At the very least as a quick fix, what you could do is send an event to your backend with the exception. For example through firebase or crashlytics. That way you can at least see stuff like (hey, the main activity does not load for 80% of our users due to a problem like (4).

While I agree with the other responses, there is one circumstance I have repeatedly encountered where this motif is marginally tolerable. Suppose someone wrote a bit of code for a class as follows:

private int foo=0;


. . .


public int getFoo() throws SomeException { return foo; }

In this circumstance, the 'getFoo()' method cannot fail - there will always be a legitimate value of the private field 'foo' to be returned. Yet someone - probably for pedantic reasons - decided that this method should be declared as potentially throwing an Exception. If you then try to call this method in a context - e.g an event handler - which does not allow an exception to be thrown, you are basically forced to use this construct (even then, I agree that one should at least log the exception just in case). Whenever I have to do this, I always at least add a big fat comment 'THIS CANNOT OCCUR' next to the 'catch' clause.

This is bad practice. Other answers have said that but I'd think it's important to step back and understand why we have exceptions in the first place.

Every function has a post-condition – a set of things that must all be true after that function executes. For example, a function that reads from a file has the post condition that the data in the file will be read from disk and returned. An exception, then, is thrown when a function has not been able to satisfy one of its post-conditions.

By ignoring an exception from a function (or even effectively ignoring it by simply logging the exception), you're saying that you're ok with that function not actually doing all the work it agreed to do. This seems unlikely – if a function does not run correctly, there is no guarantee that what follows will run at all. And if the rest of your code runs fine whether or not a particular function runs to completion, then one wonders why you have that function in the first place.

[Now there are certain cases where empty catches are ok. For example, logging is something that you might justify wrapping in an empty catch. Your application will probably run fine even if some of the logging can't be written. But those are special cases that you have to work really hard to find in a normal app.]

So the point is, this is bad practice because it doesn't actually keep your app running (the supposed justification for this style). Maybe technically the OS hasn't killed it. But it's unlikely that the app is still running properly after simply ignoring an exception. And in the worst case, it could actually be doing harm (e.g. corrupting user files, etc.).

This is bad for multiple reasons:

1. What are you doing that findViewById throws an Exception? Fix that (and tell me, because I've never seen this) instead of catching.
2. Don't catch Exception when you could catch a specific type of exception.
3. There is this belief that good apps don't crash. That's not true. A good app crashes if it must.

If an app goes into a bad state, it is much better for it to crash than for it to chug along in its unusable state. When one sees an NPE, one shouldn't just stick in a null check and walk away. The better approach is to find out why something is null and either stop it from being null, or (if null ends up being a valid and expected state) check for null. But you have to understand why the issue occurs in the first place.

As said before, general exceptions shouldn't be catched, or at least only in a few central places (usually located in framework/infrastructure code, not application code). If catching general exceptions and logging it, the application should be shut down afterwards, or at the very least user should be informed that application is potentially in a unstable state and data corruption could occur (if user chooses to continue execution). Because this is what might happen if you catch all sort of exceptions (out of memory to name one) and leaving the app in an undefined state.

IMHO it is worse to swallow exceptions and risk data integrity, data loss, or simply leaving the app in an undefined state than letting the app crash and the user knows that something went wrong and can try again. This will also lead to better issues reported (more at the root of the problem), probably fewer different symptoms than if your users start to report all kind of troubles originating from undefined application state.

After a central exception handling/logging/reporting and controlled shutdown is in place, start rewriting exception handling to catch local exceptions as specific as possible. Try to make the try{} block as short as possible.

Let me add my point of view, as a guy working in the corporate mobile development industry for more than a decade. First, some general tips on exceptions, most of them included in answers above:

• Exceptions should be used for exceptional, unexpected or uncontrolled situations, not on a regular basis throughout the code.
• A programmer must know the portions of code susceptible to throw exceptions and try-catch them, leaving the rest of the code as clean as possible.
• Exceptions should not be left silent, as a general rule.

Now, when you are not developing an app for yourself, but for a company or a corporation, it is common to face additional requirements on this topic:

• "App crashes show a poor image of the company, so they are not acceptable". Then, careful development should be performed, and catching even improbable exceptions may be an option. If so, this must be done selectively and kept in reasonable limits. And notice that development is not all about lines of code, for instance, an intensive testing process is critical in these cases. However, unexpected behaviour in a corporate app is worse than crashing. So, whenever you catch an exception in your app, you must know what to do, what to show and how the app will behave next. If you cannot control that, better let the app crash.
• "Logs and stack traces may dump sensitive information to the console. That might be used for an attacker, so for security reasons they cannot be used in a production environment". This requirement conflicts with the general rule for a developer not to write silent exceptions, so you have to find a way for it. For instance, your app could control the environment, so it uses logs and stack traces in non-production environments, while using cloud-based tools like bugsense, crashlitics or similar for production environments.

So, the short answer is that the code you found it is not a good practice example, since it is hard and costly to maintain without improving the quality of the app.

Another perspective, as someone who writes enterprise software on a daily basis, if an app has an unrecoverable error, I want it to crash. Crashing is desirable. If it crashes, it gets logged. If it crashes more than a few times in a short period of time, I get an e-mail saying that the app is crashing and I can verify that our app and all the web services we consume are still working.

So the question:

Is

try{
someMethod();
}catch(Exception e){}

good practice? No! Here are a few points:

1. The MOST important thing: This is a bad customer experience. How am I supposed to know when something bad is happening? My customers are trying to use my app and nothing works. They can't check their bank account, pay their bills, whatever my app does. My app is completely useless, but hey, at least it didn't crash! (Part of me believes this "Senior" dev gets brownie points for low crash numbers, so they're gaming the system.)

2. When I'm doing development and I write bad code, if I'm just catching and swallowing all exceptions at the top layer I have no logging. I have nothing in my console, and my app fails silently. From what I can tell, everything appears to work okay. So I commit the code... Turns out my DAO object was null the whole time, and the customer's payments were never actually updating in the DB. Whoops! But my app didn't crash, so that's a plus.

3. Playing devil's advocate, let's say I was okay with catching and swallowing every exception. It's extremely easy to write a custom exception handler in Android. If you really just have to catch every exception, you can do it in one place and not pepper try/catch all over your codebase.

Some of the developers I've worked with in the past have thought crashing was bad.

I have to assure them we want our app to crash. No, an unstable app is not okay, but a crash means we did something wrong and we need to fix it. The faster it crashes, the earlier we find it, the easier it is to fix. The only other option I can think of is allowing the user to continue in a broken session, which I equate with pissing off my userbase.