15- Atomic Objects

Jul 03, 2026 22:38 · 3:25 · English · Whisper Turbo · 2 Дисплей

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Another way to achieve threat safety is by using the atomic classes in Java.

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So in this package,

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we have a bunch of atomic classes like atomic boolean,

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atomic integer,

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atomic long and so on.

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With this atomic classes,

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we can perform atomic operations.

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For example,

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earlier you learned that incrementing a variable in Java is not atomic

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because it involves three instructions,

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get,

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increment,

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and write.

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With these atomic classes,

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we can increment or decrement a value in an atomic way.

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Let me show you.

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So in our demo class,

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we have the same code as before.

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We have a single status object that we're sharing across many different

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threads.

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Over here,

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we're creating 10 download threads.

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Each thread downloads 10 ,000 bytes.

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So once we join with all these threads and print the total

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bytes, we expect to see 100 ,000 on the terminal.

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Take a look.

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We don't see that.

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So we have a race condition now to solve

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this problem.

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We go to our download status class.

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So here we are not using synchronization.

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We are not using locks.

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We have a very simple class now to solve this problem.

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We need to change the type of this field from end to

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atomic integer and then

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we set this to a new atomic integer.

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Now in our getter

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we should return total bytes that get this will return the

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actual value and in our increment method instead of the increment

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operator we call increment and get we

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also have get an increment which returns the value first and then it will

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increment it so more accurately increment and get is equivalent

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to plus plus a where a is our variable and

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get an increment

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equivalent to a plus plus.

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Now in this case we don't want to return this value,

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we just want to increment it.

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So it doesn't really matter which method we use.

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So I would prefer to call increment

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and get because the intention is more clear.

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So that's it,

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that's all we had to do.

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Now multiple threads can modify this field concurrently without

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waiting for each other.

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Let's run the program and verify this.

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So take a look.

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There you go.

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You got 100 ,000.

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Now if you're curious how atomic types work,

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they actually use a technique called compare and swap,

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which is supported by most CPUs.

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So most CPUs can execute this operation as a single uninterruptible

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operation.

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So when we call the increment and get method,

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this atomic type is going to compare the current value with the expected

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value.

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If they're not equal,

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it's going to swap them.

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For example,

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let's say the current value of total bytes is zero and

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we want to increment it.

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So the expected value is one.

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Now this atomic type is going to compare these values because they're different,

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it's going to swap them.

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So one and zero.

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Now this entire operation is natively supported by most CPUs

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as an atomic operation.

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So if you're dealing with counter variables

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prefer atomic types to synchronization because they're faster and easier

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to use.

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