Java Threads, 3rd Edition - Multithreading, concurrency in Java. Concurrency and multithreading are some of the strong features in the Java programming language. For modern applications, we need high performance, scalability, and responsiveness. Developers use concepts of Java concurrency and multithreading to accomplish these objectives.
One of the reasons that the concepts of Java multithreading and concurrency are often used together is that they both involve running multiple things at once. But they are not quite the same. It is very important to have a grasp of Java multithreading concurrency if you are designing a real-time system, an enterprise application, a web server, or high performance softwares.
In this guide, you will learn the basic concepts of multithreading and concurrency as well as the differences between them, including their real-world benefits and uses in Java, through examples and explanations.
What is a Thread in Java?
A thread is the basic unit of execution in a program.
Java supports some degree of concurrency in a program via threads.
While being over the same memory, both threads are independent.
Developers can execute more than one tasks together by using java multithreading concurrency.
For example:
Downloading files while playing music
Dealing with multiple users in a web-based system
Processing large datasets in parallel
Threads continue promoting better performance and efficient resource management.
What is Multithreading in Java?
Multithreading allows more than one set of instructions to execute in the same process at the same time.
Multithreading and Concurrency in Java. Multithreading is a feature of java that allows concurrent execution of two or more parts of a program for maximum utilization of the CPU.
Key points about multithreading:
Several tasks are executed concurrently
Threads share resources
Improves CPU utilization
Reduces application response time
Example use cases:
Gaming applications
Video streaming
Chat applications
Banking systems
Why use a process, not a thread, in Java?
High Memory Consumption
Every process has the memory of it's own.
If you create many processes:
Memory usage becomes very high
Threads share memory:
Less memory required
Slow Creation Time
OS is very expensive in terms of process creation.
Thread creation:
Much quicker
We focus on high performance in java multithreading and concurrent so we prefer threads.
Difficult Communication
Processes communicate using:
Pipes
Sockets
IPC
This is complex.
Threads:
Directly share variables
Easy communication
Context Switching Cost
Switching between processes:
Heavy overhead
Switching between threads:
Lightweight
That's why Java concurrency and multithreading use threads.
Resource Sharing
Processes cannot easily share:
Memory
Objects
Variables
Threads:
Share resources across the same JVM very easily.
What is Concurrency in Java?
Concurrency refers to the ability to manage several tasks simultaneously.
Java concurrency and multithreading allow developers to execute multiple operations without waiting for one to finish before starting another.
Concurrency focuses on:
- Task coordination
- Resource sharing
- Synchronization
- Performance optimization
Concurrency does not always mean parallel execution.
It means handling multiple tasks efficiently.
Advantages of Java Multithreading Concurrency
- Improved performance
- Better CPU utilization
- Faster execution
- Efficient resource usage
- Responsive applications
- Background processing
- Real-time processing
Creating Threads in Java
Method 1 – Extending Thread Class
class MyThread extends Thread
{
public void run()
{
for(int i=1;i<=5;i++)
{
System.out.println(currentThread().getName()+ "Hello "+i);
}
}
}
public class TestThreading {
public static void main(String[] args) {
MyThread m1=new MyThread();//new state
MyThread m2=new MyThread();//new state
m1.start();//after call it reach to runnable state
m2.start();
}
}
Method 2 – Implementing Runnable Interface
class MyThread implements Runnable
{
@Override
public void run() {
for(int i=1;i<=5;i++)
{
System.out.println(i+"Hello");
}
}
}
class MyThread1 implements Runnable
{
@Override
public void run() {
for(int i=5;i>=1;i--)
{
System.out.println(i+"Hello");
}
}
}
public class TestRunnableInterfaceThread {
public static void main(String[] args) {
MyThread m1=new MyThread();
Thread t1=new Thread(m1);
MyThread1 m2=new MyThread1();
Thread t2=new Thread(m2);
t1.start();
t2.start();
}
}
Runnable is preferred in java multithreading concurrency because Java supports multiple interfaces but only single inheritance.
Thread Lifecycle in Java
- New
- Runnable
- Running
- Waiting
- Terminated
Understanding lifecycle is important for multithreading and concurrency in Java.
Synchronization in Java
Synchronization ensures only one thread accesses shared resources at a time.
synchronized void display() {
System.out.println("Synchronized method");
}
Synchronization helps prevent:
- Race conditions
- Data inconsistency
- Thread conflicts
It is a core concept in java multithreading and concurrency.
Inter Thread Communication
Java provides methods:
- wait()
- notify()
- notifyAll()
Used for communication between threads.
Essential in advanced java concurrency and multithreading.
Java Concurrency Utilities
Java has a great framework for concurrency:
ExecutorService
Future
Callable
CountDownLatch
Semaphore
CyclicBarrier
These utils markedly simplify concurrency programming under java multithreading.
Executor Framework
It uses executor framework to take advantage of thread pools better.
ExecutorService executor = Executors. newFixedThreadPool(3);
Benefits:
Better performance
Thread reuse
Task management
Well, it is crucial for Java enterprise-level multithreading concurrency.
Callable and Future
Callable returns results from threads.
Callable task = () -> { return 10 + 20; };
Future retrieves the result.
These are modern java concurrency and multithreading API's.
Thread Pool Concept
Thread pools are good at handling many threads.
Advantages:
Reduced overhead
Faster execution
Resource management
Commonly used in java multithreading and concurrency.
Locks in Java Concurrency
Java provides advanced locks:
ReentrantLock
ReadWriteLock
It's used for nicer control instead of sync blocks.
Hot for pure java multithreading concurrency.
Atomic Variables
Java provides atomic classes:
AtomicInteger
AtomicBoolean
AtomicLong
Used to perform thread-safe operations without synchronization.
Deadlock in Java
Deadlock is the condition in which two threads are each waiting for the other to release a resource.
Causes:
Circular waiting
Resource locking
Prevention:
Lock ordering
Timeout
Avoid nested locks
You must have the knowledge of deadlocks in multithreading and concurrency in java.
Race Conditions
A race condition happens between multiple threads with concurrent access to shared data.
Solution:
Synchronization
Locks
Atomic classes
Real Life Examples of Multithreading and Concurrency in Java
Online banking systems
Flight booking systems
Stock market applications
Video streaming platforms
Multiplayer games
E-commerce websites
Messaging apps
Search engines
They all leverage java concurrency and multithreading a lot.
Java General Concurrency and Multithreading Best Practices
Avoid shared mutable data
Use thread pools
Prefer immutable objects
Handle exceptions carefully
Minimize synchronization
Use concurrent collections
Concurrent Collections in Java
Java provides thread-safe collections:
ConcurrentHashMap
CopyOnWriteArrayList
BlockingQueue
This simplifies multithreading and concurrency in Java.
Performance Optimization Tips
Use parallel streams carefully
Avoid excessive thread creation
Monitor CPU usage
Use profiling tools
Understanding multithreading and concurrency in Java is essential for modern software development.
Using java concurrency and multithreading, developers build high-performance, scalable, and responsive applications.
Mastering java multithreading and concurrency helps in:
- Building enterprise applications
- Designing distributed systems
- Developing high-speed servers
With the right use of java multithreading concurrency, applications become faster, more efficient, and more reliable.
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Author:-
Kiran Tiwari
Kiran Tiwari
Expert trainer and consultant at SevenMentor with years of industry experience. Passionate about sharing knowledge and empowering the next generation of tech leaders.