What are three ways in which a thread can enter the waiting state? | Java Threads

A thread can enter the waiting state by the following ways:
1. Invoking its sleep() method,
2. By blocking on I/O
3. By unsuccessfully attempting to acquire an object's lock
4. By invoking an object's wait() method.
5. It can also enter the waiting state by invoking its (deprecated) suspend() method.

How do I create a Runnable with inheritance? | Java Threads

To introduce a Runnable type to an existing class hierarchy, you need to create a sub-class that declares that it implements the Runnable interface, and provide a run method to fulfil the interface. This combination of interface and inheritance means that runnable implementations can be very minor extensions of existing classes.

Do I need to use synchronized on setValue(int)? | Java Threads

It depends whether the method affects method local variables, class static or instance variables. If only method local variables are changed, the value is said to be confined by the method and is not prone to threading issues.

Can I implement my own start() method? | Java Threads

The Thread start() method is not marked final, but should not be overridden. This method contains the code that creates a new executable thread and is very specialised. Your threaded application should either pass a Runnable type to a new Thread, or extend Thread and override the run() method.

What is the difference between a threads start() and run() methods? | Java Threads

The separate start() and run() methods in the Thread class provide two ways to create threaded programs. The start() method starts the execution of the new thread and calls the run() method. The start() method returns immediately and the new thread normally continues until the run() method returns.
The Thread class' run() method does nothing, so sub-classes should override the method with code to execute in the second thread. If a Thread is instantiated with a Runnable argument, the thread's run() method executes the run() method of the Runnable object in the new thread instead.
Depending on the nature of your threaded program, calling the Thread run() method directly can give the same output as calling via the start() method, but in the latter case the code is actually executed in a new thread.

Why not override Thread to make a Runnable? | Java Threads

There is little difference in the work required to override the Thread class compared with implementing the Runnable interface, both require the body of the run() method. However, it is much simpler to make an existing class hierarchy runnable because any class can be adapted to implement the run() method. A subclass of Thread cannot extend any other type, so application-specific code would have to be added to it rather than inherited. Separating the Thread class from the Runnable implementation also avoids potential synchronization problems between the thread and the run() method. A separate Runnable generally gives greater flexibility in the way that runnable code is referenced and executed.

A Thread is runnable, how does that work? | Java Threads

The Thread class' run method normally invokes the run method of the Runnable type it is passed in its constructor. However, it is possible to override the thread's run method with your own.