Question

Which of the following is a valid way to create a thread in Java?

• A. Implementing the Runnable interface
• B. Calling the run() method directly
• C. Using the Callable interface
• D. Implementing the java class

Hint:

Always call `start()` to create a new thread. Never call `run()` directly. `start()` creates a new thread and then has that new thread execute the `run()` method.

Answer 1

The Correct Option is A

There are two primary ways to create a new thread of execution in Java:
1. By extending the `Thread` class: You create a new class that extends `java.lang.Thread` and override its `run()` method with the code you want the thread to execute. Then you create an instance of this class and call its `start()` method. 2. By implementing the `Runnable` interface: You create a new class that implements the `java.lang.Runnable` interface and provide the implementation for its single method, `run()`. Then you create an instance of this class, pass it to the `Thread` class's constructor to create a `Thread` object, and then call the `start()` method on the `Thread` object.
Let's analyze the options:
(A) Implementing the Runnable interface: This is one of the two valid ways. It is often preferred because it allows the class to extend another class, as Java does not support multiple inheritance.
(B) Calling the run() method directly: This does not create a new thread. It simply executes the `run()` method in the current thread, just like any other method call. To start a new thread, you must call the `start()` method.
(C) Using the Callable interface: `Callable` is part of the Java concurrency framework and is used with `ExecutorService`. While it's used for executing tasks in other threads, the fundamental way to create a thread is by using `Thread` or `Runnable`.
(D) Implementing the java class: This is too vague to be a correct answer.
Therefore, implementing the `Runnable` interface is a valid way to create a thread.