In our previous blog, we talked mostly theroretical concepts about a ThreadPoolExecutor.

In this blog we will start with a ThreadPoolExecutor with a single thread.

What is a SingleThreadExecutor

• It has only a single thread available to execute the task, so can only execute one task at a time.
  
• The single thread executor is ideal for creating an event loop.
  
• Following attributes are set in a ThreadPoolExecutor for a single thread executor
  • corePoolSize = 1
  • maximumPoolSize = 1
  • keepAliveTime = 0 milliseconds.

When would you need it

• When we want to run some task in other thread, but only one instance at a time
• E.g. some processing where order of execution matters, and we want to execute task2 only after task1 is completed.

Code Examples

For all our code examples – we will use this “dummy” Runnable class (MyDummyTask.java)

It does nothing, to be honest – just does a Thread.sleep for a second.

Executing a single task in a different thread

Here is the code to create a single thread executor service

On Executing it you will see an output like this

Executing multiple tasks one by one in a Single Thread Executor

We can also execute mutliple tasks on single thread executor service. It will just queue all the tasks and execute them in a sequential ordered way. Check the code example below

If you look at the output of the execution, you can see all tasks execute one by one – Task 1 after Task2, Task3 after Task2, and so on.

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Code located at – SingleThreadExecutorDemo.java and MyDummyTask.java

In future blogs we will cover more different types of ThreadPoolExecutor, along with code examples