Java Program to Implement Multi Threading and Exception Handling

by

Aim:

To implement multi threading and exception handling using java program.

CREATION OF THREADING IN JAVA:

How to create thread

There are two ways to create a thread:

  1. By extending Thread class
  2. By implementing Runnable interface.

Thread class:

Thread class provide constructors and methods to create and perform operations on a thread.Thread class extends Object class and implements Runnable interface.

Commonly used Constructors of Thread class:

  • Thread()
  • Thread(String name)
  • Thread(Runnable r)
  • Thread(Runnable r,String name)

Commonly used methods of Thread class:

  1. public void run(): is used to perform action for a thread.
  2. public void start(): starts the execution of the thread.JVM calls the run() method on the thread.
  3. public void sleep(long miliseconds): Causes the currently executing thread to sleep (temporarily cease execution) for the specified number of milliseconds.
  4. public void join(): waits for a thread to die.
  5. public void join(long miliseconds): waits for a thread to die for the specified miliseconds.
  6. public int getPriority(): returns the priority of the thread.
  7. public int setPriority(int priority): changes the priority of the thread.
  8. public String getName(): returns the name of the thread.
  9. public void setName(String name): changes the name of the thread.
  10. public Thread currentThread(): returns the reference of currently executing thread.
  11. public int getId(): returns the id of the thread.
  12. public Thread.State getState(): returns the state of the thread.
  13. public boolean isAlive(): tests if the thread is alive.
  14. public void yield(): causes the currently executing thread object to temporarily pause and allow other threads to execute.
  15. public void suspend(): is used to suspend the thread(depricated).
  16. public void resume(): is used to resume the suspended thread(depricated).
  17. public void stop(): is used to stop the thread(depricated).
  18. public boolean isDaemon(): tests if the thread is a daemon thread.
  19. public void setDaemon(boolean b): marks the thread as daemon or user thread.
  20. public void interrupt(): interrupts the thread.
  21. public boolean isInterrupted(): tests if the thread has been interrupted.
  22. public static boolean interrupted(): tests if the current thread has been interrupted.

Runnable interface:

The Runnable interface should be implemented by any class whose instances are intended to be executed by a thread. Runnable interface have only one method named run().

1. public void run(): is used to perform action for a thread.Code language: JavaScript (javascript)

Starting a thread:

start() method of Thread class is used to start a newly created thread. It performs following tasks:

  • A new thread starts(with new callstack).
  • The thread moves from New state to the Runnable state.

When the thread gets a chance to execute, its target run() method will run.

1) Java Thread Example by extending Thread class

class Multi extends Thread{  
public void run(){  
System.out.println("thread is running...");  
}  
public static void main(String args[]){  
Multi t1=new Multi();  
t1.start();  
}  
}  Code language: JavaScript (javascript)

2) Java Thread Example by implementing Runnable interface

class Multi3 implements Runnable{  
public void run(){  
System.out.println("thread is running...");  
}  
  
public static void main(String args[]){  
Multi3 m1=new Multi3();  
Thread t1 =new Thread(m1);  
t1.start();  
}  
}  Code language: PHP (php)

If you are not extending the Thread class,your class object would not be treated as a thread object.So you need to explicitely create Thread class object.We are passing the object of your class that implements Runnable so that your class run() method may execute.

Aim:

To implement multi threading and exception handling using java program.

Algorithm:

  1. Declare class Th1 extend from the thread.
  2. Declare try, catch with data.
  3. Declare another 2 classes Th2, Th3 define method.
  4. Declare main classes Th demo and create object T1, T2 and t3 for each class. Access it.
  5. Display the result.

Program:

import java.io.*;
class th1 extends Thread {
private String name;
th1(String n)
{
this.name=n;
}
public void run()
{
try {
if(this.name=="th2")
{
th2 A=new th2();
A.compute();
System.out.println("THREAD "+this.name+ " calculates sum of first 5 integers="+A.result  );
}
if(this.name=="th3")
{
th3 A=new th3();
A.compute();
System.out.println("THREAD "+this.name+ " calculates product of first 5 integers="+A.result  );
}
}
catch (Exception e) {
System.out.println("Exception is caught");
}
}
}
class th2{
int result=0;
void compute()
{
for(int i=1;i<=5;i++)
{
result=result+i; 
}
}
}
class th3{
int result=1;
void compute()
{
for(int i=1;i<=5;i++)
{
result=result*i; 
}
}
}
public class Main
{
public static void Main(String []args){
String a="th2";
String b="th3";
th1 r1= new th1(a);
th1 r2=new th1(b);
r1.start();
r2.start();
}
}

Execution:

THREAD th3 calculates product of first 5 integers = 120
THREAD th2 calculates sum of first 5 integers = 15

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