01_Thread.md

Java Thread

Concurrency

• Concurrency
  • Logical
  • Single Core / Multi Core
• Parallel
  • Physical
  • Multi Core

Since Java runs on the JVM (Java Virtual Machine), you don't need to worry about the physical aspects!

What is a Java Thread?

• Process

  : A program that operates independently (Eclipse, Messenger, etc)

• Thread

  : A small unit of execution that constitutes a Process (Messenger = chat + file transfer)

• Multi-process

  : Running multiple processes simultaneously

• Multi-thread

  : Multiple threads operating simultaneously within a single process

Creating a Java Thread

Method 1) Implementing the Runnable interface

• Runnable interface

  ex)

  package virus;
  
  public class CoronaRunnable implements Runnable{
  
  	int num;
  	public CoronaRunnable() {}
  	public CoronaRunnable(int num) {
  		this.num = num;
  	}
  	@Override
  	public void run() {
  		for (int i =0 ; i< 10000 ; i++) {
  			int j = i*100;
  		}
  		System.out.println(num);
  	}
  }

  
  

• Test

  package app;
  
  import virus.CoronaRunnable;
  
  public class CoronaThreadTest {
  	public static void main(String[] args) {
  		for (int i = 0 ; i <1000 ; i++) {
  			CoronaRunnable cr = new CoronaRunnable(i);
  			Thread t = new Thread(cr);
  			// Start the Thread
  			t.start();
  		}
  	}
  }

Method 2) Extending the Thread class

• Thread class

  ex)

package virus;

public class CoronaThread extends Thread{ int num;

public CoronaThread() {}
public CoronaThread(int num) {
	this.num = num;
}

@Override
public void run() {
	for (int i = 0 ; i < 10000 ; i++) {
		int j = i*100;
	}
	System.out.println(num);
}

}

<br>

- Test

```java
import virus.CoronaRunnable;
import virus.CoronaThread;

public class CoronaThreadTest {
	public static void main(String[] args) {
		for (int i = 0 ; i <1000 ; i++) {
			CoronaThread ct = new CoronaThread(i);
			ct.start();
		}
	}
}

Memory Structure When Running a Thread