Threads in java with example

Read this article to know what is thread and what is the lifecycle of thread in java. Threads concept introduced in java to achieve multiprocessing. Thread represents a separate path of program execution. All threads are running on top of the Main thread in java. This main thread is called daemon thread.

Explanation: A thread represents a separate path of execution of a group of statements. In a Java program, if we write a group of statements, then these statements are executed by JVM one by one. This execution is called thread, because JVM uses a thread to execute these statements. This means in every Java program there is thread is running internally.

Let us see the below program to find the thread used by JVM to execute the statements: 
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
package com.javatbrains.threads;

public class CurrentThread {

      public static void main(String[] args) {
        System.out.println("Let us find the current thread");
        Thread t = Thread.currentThread();
        System.out.println("Current Thread: "+t );
        System.out.println("Its name= "+t.getName());
      }

}

OutPut:
      Let us find the current thread
      Current Thread: Thread[main,5,main]
      Its name= main

In the above program, currentThread () is a static method in Thread class. So, we called it as Thread.currentThread() . Then method gave an object t of Thread class, it displayed its contents as.
1
Thread[main,5,main]

In the above line first main indicates the name of the thread running the current code.We get 5 which is a number representing the priority of the thread. Every thread will have a priority number associated with it. The next main indicates the thread group name to which this thread belongs. A thread group represents a group of threads as a single unit.

Thread Life Cycle

A thread has many states in its life cycle. While starting from the birth of a thread, till its death, a thread exists in different states which are collectively called "Thread Life Cycle".

 A thread will born when it is created using Thread class as,
1
Thread t =  new Thread();

Then the thread goes into runnable state when start() method is applied on it. yield() method may pass a thread briefly, but the thread will be still in runnable state only.

From runnable state, a thread may get into not runnable state, when sleep(), or wait() methods act on it. A thread may be occasionally blocked on some I/O device where it is expecting some I/O from the user. After coming out from not- runnable state, again the thread comes back to runnable state.

Finally, a thread is terminated from memory only when it comes out of run method.

A thread represents execution of statements. The way the statements are executed is of two types.
                                    1.           Single Tasking
                                    2.           Multi Tasking

Single Tasking

 A task means doing some calculation, processing,etc. Generally a task involves execution of a group of statements, for example executing a program.

In single tasking, only one task is given to the processor ar a time. This means we are wasting a lot of processor time and microprocessor has to sit idle without any job for a long time. This is the drawback in single tasking.

Multi Tasking

To use the processor time in an optimum way, we can give it several tasks at a time. This is called multi tasking. Multi tasking is of two types:
                     1.   Process-based multi tasking
                     2.   Thread-based multi tasking

Process-based multi tasking:
                  

The above diagram represents the round robin method. There are 4 tasks are present. Processor time will divide by 4 means each task takes 1/4 milliseconds time. First task executes in 1/4 milliseconds time, then it will come to next task2. But, this task not executed in expecting time that till come to task3. Task 3 will get execute and it will save in temporary memory. Similarly it will spent the same time in task4. Then it comes into first task and start executing where it left that task earlier. This is called 'round robin' method.

The main advantage of multi tasking is to use the processor time in a better way. We are engaging most of the processor time and it is not sitting idle. In this way, we can complete several tasks at a time, and thus achieve good performance.

Thread-based multi tasking:
In Process-based multi tasking, several programs are executed at a time, by the microprocessor. Thread-based multi tasking, several parts of the same program is executed at a time, by the microprocessor.
         
In the above diagram, program has two parts. These parts may represents two separate block of code or two separate methods containing code. Each part may perform a separate task. The processor should execute the two parts simultaneously. So the processor uses 2 separate threads to execute these two parts.

Achieving multi tasking with threads has one advantage, i.e. Since the threads are light weight processes, They use minimum resources of the system.

Uses of Threads:

Threads can be used for multiple processes. Some of the uses of threads are,
              1.  Threads are mainly used in server-side programs to serve the needs of multiple clients on a network or Internet.
              2. Threads are also used to create games and animations. 
       Animations means moving the objects from one place to another. In many games, generally we have to perform more than one task simultaneously.

Do you know?
Location: Bengaluru, Karnataka 560017, India

Comments

Post a Comment

Popular posts from this blog

Hibernate auto increment with example

In previous example we learn how to map java object with database table for manually(not using auto increment) assigned all the values.  To create primary key auto increment application by using hibernate mapping(hbm.xml) or using annotations continue reading this article.  W e need to create a database and create an employee table by using the below query. Table: CREATE table EMPLOYEE( eid integer ( 10 ) primary key not null , firstname varchar ( 30 ), lastname varchar ( 30 ), designation varchar ( 30 ), salary double( 10 , 2 )); Here, we will create a bean/POJO (Plain Old Java Object) class of employee. Employee.java: package com . javatbrains . hibernate ; import java.io.Serializable ; /*This is the POJO class. It contains only Getter and Setter methods*/ public class Employee implements Serializable { private static final long serialVersionUID = - 75885815725314443L ; private int eid ; ...
Read more

how to count the page views by using JSP

To count no.of page's are viewed by user in your application is a challenge in real time application. In this page we will see how to count the page views when user has viewed the page.           Here, we will do one example how many times user has visited each page in our application. In this post we will come to know, how to count the total application page views as well as individually each pages count.           Let us assume my web application name is "Page Counter". For creating the web application in eclipse IDE, Click here . This Page Counter contains three pages, assume that are the different pages in an application. But, there is the link between each other files for navigating from one page to another. Also it will show the total pages view count and individual page view count in all the pages. Let us see, below is my first jsp file,         ...
Read more

Multithreading in java with example

Multithreading  is one of the most important concept in core java. In this article we will learn what is multithreading? , what is the use of it? and What is the use of Synchronization and when to use it?  with detailed examples. At a time, two or more threads are accessing the same object is called as Multithreading  in Java .  First, we will create two threads for two objects. It is also possible to run two or more threads on a single class object. In this case, there is a possibility to get unreliable results. If the two threads are perform same task, then they need same object to be executed each time. For your better understanding, take an example of any reservations like, railway, movie ticket booking,etc. Let us think only one berth is available in a train and two passengers are asking for that berth. The first person has sent a request to allocate that ticket/berth to him. At the same time, the second person also sent a request to allocate that ...
Read more

How to retrieve data from table by using JDBC with example

To retrieve data from mysql data table by using jdbc, we need to confirm weather which table data we need to retrieve. To confirm open your mysql and view all database names by using the ' show databases ' commands in mysql. Then select which is your database name from showing list of database names, by using the ' use <database name> ' command in mysql. Then we need to see all your existing tables by executing the ' show tables ' command. This command gives you the list of existing tables in your selected database. You need to use existing table only you can follow with that. But, here we will see with entirely new which is not existing in mysql database. Now, We will create simple mysql table with minimal columns. create table emp(eno integer(10), ename varchar(30), sal float); The above command creates a new table, we will move further to insert records into emp table by executing the insert which we mentioned in the below. ...
Read more

Prime, Fibonacci and Factorial number with example in java

Prime number, Fibonacci series and Factorial number programs are most commonly asked questions in interview. Read this article to know what is and how to write programs for prime number, fibonacci series and factorial number. Prime Number: prime number is natural number greater than 1 that has no positive divisor other than 1 and itself. A natural number greater than 1 is not a prime number, is called Composite number . For example, 7 is a prime number. Because it can divide with 1 and 7 only. Where as 8 is composite number. Since it has the divisor 2 and 4 in addition to the 1 and 8. The below example represents the finding the passing number is prime number or not. If the passing number is prime number it will print true otherwise it will print false. package com . javatbrains . practice ; public class PrimeNumber { public boolean isPrimeNumber ( int number ) { if ( number <= 1 ) return false ; // There's only one ...
Read more

How to insert images into database using JDBC?

How to insert images into database table by using JDBC? To know about these topic follow the below lines,           Before going to write a JDBC program for inserting images into database table, we need to create a specific table for inserting images column datatype. For creating the database table, execute the below command in MySQL command prompt. 1 2 3 4 CREATE TABLE ` images ` ( ` image_id ` int ( 11 ) NOT NULL AUTO_INCREMENT, ` image_flag ` int ( 11 ) NOT NULL , ` image ` longblob NOT NULL , PRIMARY KEY ( ` image_id ` ));           After executing the above query in MySQL command prompt, execute the below query to know weather the above table query is created or not. 1 Show tables;            When you have executed the above query that will show you the list of table which all exists in the current database. Current tab...
Read more

How to sort list of objects in java with examples

We could achieve list of objects sorting in java by using sort() method which is available under Collections class as well as by using Comparable and Comparator  interfaces. Comparable and Comparator are two interfaces in java used to sort list of objects. These interfaces are available under java.util package along with Collections  class and other classes and interfaces. Comparable interface contains the method of       public int compareTo(Object obj) Comparator interface contains the method of       public int compare(Object obj1, Object obj2) The compare() and compareTo() methods will return negative integer(-1), or zero(0) or positive integer(1). When the first obj1 is less than obj2 method will return negative integer. When obj1 is equals to obj2 will return zero and when obj1 is grater than obj2 it will return positive integer. If it's objects are stored in any Collection classes like ArrayList, H...
Read more

String interview questions and answers

String interview questions and answers are placed the current post as of my experience in interviews. This will helps who are trying to attend interview as fresher as well as experience. If any one is facing any other questions which are not present in the current page, please drop me an email to " subbareddynallamachu@gmail.com ".  Q1:  String is a class or data type? A: String is a class in java.lang package. But, in java, all classes are also are considered as data types. So we can take String as data type also. Q2:  What is the difference between == and equals() methods in java? A: == operator compares the references of the String object. It does not compare the content of the object. equals() method compares the contents. While comparing the Strings, equals method should be used as it yields the correct result. Q3:  What is String constant pool? A: String constant pool is a separate block of memory where the String objects are held by JVM....
Read more

Exception in thread "main" java.lang.NoClassDefFoundError: javax/transaction/SystemException

Exception in thread "main" java.lang.NoClassDefFoundError: javax/transaction/SystemException error we got in Hibernate 4.3 to work with my MySQL database. We are using hibernate code generation tool in Eclipse and we are able to connect to the database using the Hibernate configuration file. When we try to run code in my Main class application is connecting to the database, but transaction is failing and we got the following error: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Exception in thread "main" java . lang . NoClassDefFoundError : javax / transaction / SystemException at java . lang . Class . forName0 ( Native Method ) at java . lang . Class . forName ( Unknown Source ) at org . jboss . logging . Logger . getMessageLogger ( Logger . java : 2248 ) at org . jboss . logging . Logger . getMessageLogger ( Logger . java : 2214 ) at org . hibernate . cfg . Configuration .< clinit >( Configuration . java : 184 ) at be . comp . permanenti...
Read more

Store file into table by using JDBC with example

To store large data files or text files into database table, we will use CLOB (Charecter Large Object) datatype of SQL . By using CLOB it is possible to save entire text book or a file or resume into a column of data table. If your using MySQL database instead of CLOB use LONGTEXT to save file into datatable. For saving files into a data table, we need to create one table which will contains a column type as CLOB to store files. Here, is the query to create a data table. 1 2 3 4 create table myfiles( file_id int ( 10 ), file_name varchar ( 30 ), file_type LONGTEXT); Once table creation completes, these table contains the 3 columns one is file_id represents the file id, file_name represents the name of the file and finally file_type will get save entire file into the table column. Now, we will move to write a JDBC program which will saves the file into the newly creating table. Here is the JDBC program, 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16...
Read more