What is the difference between a process and a thread, and when can one be used instead of the other?

A process is an isolated execution unit with its own address space, resources, and threads. A thread is the smallest unit of execution within a process, sharing memory and resources with other threads.

Main differences:

• Processes are isolated from each other, while threads within the same process share memory.
• Creating and switching between processes is more resource-intensive than between threads.
• Threads are convenient for parallel execution of tasks that require shared access to data.

When to use:

• Processes are suitable for isolation, such as running independent applications or services where security and stability are important.
• Threads are suitable for parallel computations within a single application, where data sharing and quick switching are needed.

Example: In Java, threads (Thread, ExecutorService) are used for parallel data processing within an application, while processes (ProcessBuilder) are used to launch separate applications or services.