Threads in java

Multithreading

Running multiple threads concurrently within a program

Thread

sequence of instructions in a process

Process

A program in execution with its own memory space

Concurrency

Managing multiple tasks at once (not necessarily parallel)(each thread execution is seperated to others threads execution

Parallelism

Executing multiple tasks simultaneously on multiple cores

Thread class

Class used to create a thread by extending it

interrupt

doesn’t stop a thread ,it sends an interrupt request, to support the request we should check it

Runnable interface

Interface to define a task for a thread (run method)

run()

Method containing code executed by a thread

start()

Method that starts a new thread and calls run()

Thread lifecycle

New, Runnable, Running, Blocked/Waiting, Terminated

sleep()

Pauses a thread for a specified time

join()

makes a thread Wait for another thread to finish execution(block the current thread untilthe other has finished)

yield()

Hints scheduler to give other threads a chance

Daemon thread

Background thread that runs until all user threads finish

User thread

Thread that keeps JVM running

Synchronization

Controlling access to shared resources to avoid conflicts

synchronized keyword

Locks a method or block for thread-safe execution

Critical section

Code accessing shared resources

Race condition

Multiple threads competing to modify shared data causing inconsistency

Deadlock

Threads waiting indefinitely for each other’s resources

Livelock

Threads keep responding but make no progress

Thread safety

Code that works correctly with multiple threads

wait()

Makes thread wait and releases lock

notify()

Wakes one waiting thread

notifyAll()

Wakes all waiting threads

volatile keyword

Ensures visibility of shared variables across threads

Atomic operations

Operations completed without interruption

Executor framework

Manages thread pools and task execution

Thread pool

Group of reusable threads for efficiency

Callable interface

Like Runnable but returns a result

Future object

Holds result of asynchronous computation

Lock

methodes: lock; unlock

volatile

volatile key-word guarantees the change to a field is visible accross threads