Thread is a lightweight process. Threads exist within a process. So every process has at least one thread. Thread in Java is represented by java.lang.Thread class. Every Java application has one or several threads.

• Threads are lightweight. Creating a new thread requires fewer resources than creating a new process.
• Threads share process’s resources like memory space.
• Context switching between threads is usually less expensive than switching between processes.
• Cost of intercommunication between threads is relatively low than that of communication between processes.

There are two ways to create thread in Java:

• By implementing the Runnable interface.
• By extending java.lang.Thread class.