7- The finally Block

Jun 18, 2026 04:35 · 4:10 · English · Whisper Turbo · 2 Højttalere

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Forelæsningsindeks

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S… Speaker 2 (7- The finally Block)

Let's imagine this file exists,

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so we successfully open it for reading,

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but something goes wrong when we try to read data from this file.

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This could happen because of a hardware problem.

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Now we have a problem in this code.

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The problem is that we have opened this file for reading,

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but nowhere we have closed it.

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File handles are operating system resources,

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so whenever we get them,

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we should always release them.

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Otherwise, other processes may not be able to access these resources.

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So somewhere in this code,

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we should write reader .close.

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Now there's a problem with this implementation.

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Can you tell?

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The problem is that if this line throws an exception,

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the runtime will pass the control to this catch block,

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so this line will never get executed.

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Now what if we put this line after our try catch block?

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Now the reader variable is not recognized

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because we have declared it inside this try block,

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so it's only accessible in this block.

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But let's not worry about it for a second.

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The problem with this implementation is that sometime in the future,

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another developer might come here and write some extra code

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and this code may throw an exception.

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Again,

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our reader is not going to get closed.

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The proper way to handle this kind of scenarios is to use the finally

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block.

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So right after the catch block,

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we type finally

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Now in this block we can release external resources like file handles,

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database connections,

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network connections and so on.

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So here we should type reader .close

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but once again reader is not recognized because it's

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only accessible in the try block.

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To solve this problem we need to declare this before our try block.

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So we type file reader reader

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and then set it over here.

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And by the way,

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we cannot use var over here,

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because we can use var only when we set this to a new instance

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of a class.

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So the compiler knows that this object is an instance of the file

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reader class.

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In this case,

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we're not initializing this variable.

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So the compiler doesn't know what is the type of this variable.

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So,

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let's type file reader.

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Now,

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we have a compilation error.

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variable reader might not have been initialized.

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Because in Java,

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before we can access an object,

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we should always initialize it.

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So if this line doesn't get executed,

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if it throws an exception,

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we'll try to use an uninitialized object.

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To solve this problem,

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we need to explicitly set this to null.

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The compilation error is gone,

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now we have a different kind of error,

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we'll talk about that in a second,

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but first let's add an if statement.

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We want to call the close method only if the reader is not null.

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So if reader is not null,

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then close it.

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But what is this compilation error?

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On handle exception,

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IO exception.

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So the close method may also throw an IO exception.

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To solve this problem,

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we need to wrap this inside the try catch block.

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So we put the caret over here,

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press alt and enter,

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and then surround with try catch.

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So here's the final result.

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Now, this code looks really ugly.

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I have to admit that we have a much better exception handling structure in C sharp.

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Now, that aside,

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what I want you to take away here is that this find in the block will

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always get executed,

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whether we have an exception or not.

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If we don't have an exception,

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all the code inside the try block will get executed and

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then the runtime will pass control to the find in the block.

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If one of these lines throws an exception

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one of our catch blocks will get executed and then the finally block

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will get executed.

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So the finally block will always get executed no matter what.

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Now,

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this implementation is really ugly.

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In the next video,

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I'm going to show you a better way to release external resources.

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