7- The finally Block

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

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Lecture Index

0:03

S… Speaker 2 (7- The finally Block)

Let's imagine this file exists,

0:05

S… Speaker 2 (7- The finally Block)

so we successfully open it for reading,

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S… Speaker 2 (7- The finally Block)

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

0:11

S… Speaker 1 (7- The finally Block)

This could happen because of a hardware problem.

0:13

S… Speaker 1 (7- The finally Block)

Now we have a problem in this code.

0:15

S… Speaker 2 (7- The finally Block)

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

0:19

S… Speaker 2 (7- The finally Block)

but nowhere we have closed it.

0:21

S… Speaker 2 (7- The finally Block)

File handles are operating system resources,

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S… Speaker 2 (7- The finally Block)

so whenever we get them,

0:25

S… Speaker 2 (7- The finally Block)

we should always release them.

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S… Speaker 2 (7- The finally Block)

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

0:30

S… Speaker 2 (7- The finally Block)

So somewhere in this code,

0:33

S… Speaker 2 (7- The finally Block)

we should write reader .close.

0:36

S… Speaker 1 (7- The finally Block)

Now there's a problem with this implementation.

0:38

S… Speaker 1 (7- The finally Block)

Can you tell?

0:39

S… Speaker 1 (7- The finally Block)

The problem is that if this line throws an exception,

0:43

S… Speaker 2 (7- The finally Block)

the runtime will pass the control to this catch block,

0:47

S… Speaker 2 (7- The finally Block)

so this line will never get executed.

0:49

S… Speaker 2 (7- The finally Block)

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

0:52

S… Speaker 1 (7- The finally Block)

Now the reader variable is not recognized

0:57

S… Speaker 2 (7- The finally Block)

because we have declared it inside this try block,

1:00

S… Speaker 2 (7- The finally Block)

so it's only accessible in this block.

1:02

S… Speaker 2 (7- The finally Block)

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

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S… Speaker 2 (7- The finally Block)

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

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S… Speaker 2 (7- The finally Block)

another developer might come here and write some extra code

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S… Speaker 2 (7- The finally Block)

and this code may throw an exception.

1:14

S… Speaker 1 (7- The finally Block)

Again,

1:15

S… Speaker 2 (7- The finally Block)

our reader is not going to get closed.

1:18

S… Speaker 1 (7- The finally Block)

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

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S… Speaker 1 (7- The finally Block)

block.

1:22

S… Speaker 1 (7- The finally Block)

So right after the catch block,

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S… Speaker 2 (7- The finally Block)

we type finally

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S… Speaker 2 (7- The finally Block)

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

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S… Speaker 2 (7- The finally Block)

database connections,

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S… Speaker 2 (7- The finally Block)

network connections and so on.

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S… Speaker 2 (7- The finally Block)

So here we should type reader .close

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S… Speaker 2 (7- The finally Block)

but once again reader is not recognized because it's

1:42

S… Speaker 2 (7- The finally Block)

only accessible in the try block.

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S… Speaker 2 (7- The finally Block)

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

1:48

S… Speaker 1 (7- The finally Block)

So we type file reader reader

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S… Speaker 1 (7- The finally Block)

and then set it over here.

1:56

S… Speaker 2 (7- The finally Block)

And by the way,

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S… Speaker 2 (7- The finally Block)

we cannot use var over here,

1:59

S… Speaker 2 (7- The finally Block)

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

2:03

S… Speaker 1 (7- The finally Block)

of a class.

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S… Speaker 2 (7- The finally Block)

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

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S… Speaker 1 (7- The finally Block)

reader class.

2:08

S… Speaker 1 (7- The finally Block)

In this case,

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S… Speaker 2 (7- The finally Block)

we're not initializing this variable.

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S… Speaker 2 (7- The finally Block)

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

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S… Speaker 1 (7- The finally Block)

So,

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S… Speaker 1 (7- The finally Block)

let's type file reader.

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S… Speaker 1 (7- The finally Block)

Now,

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S… Speaker 2 (7- The finally Block)

we have a compilation error.

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S… Speaker 2 (7- The finally Block)

variable reader might not have been initialized.

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S… Speaker 2 (7- The finally Block)

Because in Java,

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S… Speaker 2 (7- The finally Block)

before we can access an object,

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S… Speaker 2 (7- The finally Block)

we should always initialize it.

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S… Speaker 2 (7- The finally Block)

So if this line doesn't get executed,

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S… Speaker 2 (7- The finally Block)

if it throws an exception,

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S… Speaker 2 (7- The finally Block)

we'll try to use an uninitialized object.

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S… Speaker 1 (7- The finally Block)

To solve this problem,

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S… Speaker 2 (7- The finally Block)

we need to explicitly set this to null.

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S… Speaker 1 (7- The finally Block)

The compilation error is gone,

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S… Speaker 2 (7- The finally Block)

now we have a different kind of error,

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S… Speaker 2 (7- The finally Block)

we'll talk about that in a second,

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S… Speaker 2 (7- The finally Block)

but first let's add an if statement.

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S… Speaker 2 (7- The finally Block)

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

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S… Speaker 2 (7- The finally Block)

So if reader is not null,

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S… Speaker 2 (7- The finally Block)

then close it.

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S… Speaker 2 (7- The finally Block)

But what is this compilation error?

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S… Speaker 1 (7- The finally Block)

On handle exception,

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S… Speaker 2 (7- The finally Block)

IO exception.

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S… Speaker 2 (7- The finally Block)

So the close method may also throw an IO exception.

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S… Speaker 1 (7- The finally Block)

To solve this problem,

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S… Speaker 2 (7- The finally Block)

we need to wrap this inside the try catch block.

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S… Speaker 2 (7- The finally Block)

So we put the caret over here,

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S… Speaker 2 (7- The finally Block)

press alt and enter,

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S… Speaker 2 (7- The finally Block)

and then surround with try catch.

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S… Speaker 1 (7- The finally Block)

So here's the final result.

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S… Speaker 1 (7- The finally Block)

Now, this code looks really ugly.

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S… Speaker 2 (7- The finally Block)

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

3:29

S… Speaker 1 (7- The finally Block)

Now, that aside,

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S… Speaker 2 (7- The finally Block)

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

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S… Speaker 1 (7- The finally Block)

always get executed,

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S… Speaker 2 (7- The finally Block)

whether we have an exception or not.

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S… Speaker 2 (7- The finally Block)

If we don't have an exception,

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S… Speaker 2 (7- The finally Block)

all the code inside the try block will get executed and

3:44

S… Speaker 2 (7- The finally Block)

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

3:46

S… Speaker 1 (7- The finally Block)

If one of these lines throws an exception

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S… Speaker 2 (7- The finally Block)

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

3:54

S… Speaker 1 (7- The finally Block)

will get executed.

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S… Speaker 2 (7- The finally Block)

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

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S… Speaker 1 (7- The finally Block)

Now,

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S… Speaker 2 (7- The finally Block)

this implementation is really ugly.

4:02

S… Speaker 2 (7- The finally Block)

In the next video,

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S… Speaker 2 (7- The finally Block)

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

This transcript was generated by AI (automatic speech recognition). May contain errors — verify against the original audio for critical use. AI policy

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