18- Concurrent Collections

Jul 03, 2026 22:45 · 2:37 · English · Whisper Turbo · 2 Głośniki

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S… Speaker 1 (18- Concurrent Collections)

Synchronized collections achieve thread safety by using locks.

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So when a thread gets access to a synchronous collection,

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the entire collection gets locked and other threads have to wait.

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This works well for most cases,

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but it can have a negative impact on the performance and scalability as

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the number of threads and concurrent operations increase.

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In those situations we can use concurrent collections in Java.

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These classes use the partitioning technique to allow concurrency.

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So they divide their data into segments and different threads can concurrently

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work with different segments,

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but only one thread at a time can access a given segment.

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So concurrent collections are faster than synchronized collections because they

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don't use synchronization.

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These classes are declared in the java .util .concurrent package.

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For example,

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we have concurrent hash map,

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we have concurrent link deck,

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which is a double ended queue implemented using a linked list.

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We have concurrent map and so on.

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So let's take a look at an example.

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If you want to create a regular hash map,

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we write map of integer and

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string.

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We call it map and set it to a new hash map.

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This is a regular hash map where our keys are integers and our values

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are strings.

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Here we can call map .put to add an entry

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like 1 and a.

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We can call map .get to get the value

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associated with the key.

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We can call map .remove and so on.

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Now this is a regular hash map implementation that

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is not thread safe.

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So if it's going to get access only by a single thread,

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it's perfectly fine.

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But if you want to share this across many different threads,

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we're going to have problems.

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Now to solve this,

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all we have to do is to replace the hash map with the

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concurrent hash map.

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That's all we had to do.

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Everything else in our code stays the same.

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Because this map is an interface,

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and hash map and concurrent hash map are two

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different implementations of this interface.

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So by programming against interfaces,

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we reduce the impact of changes in our applications.

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We simply substitute one implementation with another.

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Everything else stays the same.

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Again,

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I cannot emphasize the importance of interfaces enough.

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A lot of developers don't understand interfaces.

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They think they do,

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but honestly,

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they don't.

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So if you want to have a better understanding of interfaces and their power,

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watch the second part of this series.

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It will change how you think about building software.

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