Problem:

• In a single threaded program these instructions will be executed one by one.
• The time-consuming sections of the code can freeze the entire application

Solution:

• Figure out the time-consuming tasks and decide if they can be run separately.
• If yes, run such task(s) in separate threads.

Multi Threading is the ability of CPU to perform different tasks concurrently.

Process:

• Process is an instance of program execution.
• When you enter an application, it's a process.
• The OS assigns its own Stack & Heap Memory area.

Thread:

• Thread is a lightweight process.
• It is a unit of execution within a given program.
• A single process may contain multiple threads.
• Each thread in the process shares the memory and resources.

States of Thread:

• New State: When we call the start() method.
• Active State: We have two types: Runnable & Running.
• Blocked State: Waiting for some I/O execution to occur.
• Terminated State: The thread completed its execution.

Concurrency Vs Parallelism:

• Not Concurrent, Not Parallel

  • CPU Core: ---Task1-----Task2-----

• Concurrent, Not Parallel

  • CPU Core: ---Task1---Task2---Task1----Task1----

• Not Concurrent, Parallel

  • CPU Core1: ----Task1----
  • CPU Core2: ----Task2----

• Concurrent, Parallel

  • CPU Core1: ---Task1---Task2---Task1----Task1----
  • CPU Core2: ---Task3---Task4---Task3----Task4----