Tutorial Java: 2016

Lets discuss some interesting programs on this keyword.
Now its time to practice some programs on this keyword.
Try to guess the output of the following java programming questions on this keyword.
If you want explanations for all the programs please go through this keyword interview questions on java

Java Quiz on this keyword part #1

Program #1: Java interview programming question on this keyword.

package thiskeywordinterviewprograms.java;
public class ThisDemo {
int a;
int b;
ThisDemo(int a, int b){
a=a;
b=b;
}
public static void main(String[] args) {
ThisDemo obj = new ThisDemo(10, 20);
System.out.println(obj.a);
System.out.println(obj.b);
}
}

Program #2: Java interview programming question on this keyword.

package thiskeywordinterviewprograms.java;
public class ThisDemo {
int a;
int b;
ThisDemo(int a, int b){
this.a=a;
this.b=b;
}
public static void main(String[] args) {
ThisDemo obj = new ThisDemo(10, 20);
System.out.println(obj.a);
System.out.println(obj.b);
}
}

Program #3: Java Interview programming example on this keyword.

What will be the output of the below program

package thiskeywordinterviewprograms.java;
public class ThisDemo {
int a;
int b;
ThisDemo(int a, int b){
this.a=a;
this.b=b;
}
public static void main(String[] args) {
ThisDemo obj = new ThisDemo();
System.out.println(obj.a);
System.out.println(obj.b);
}
}

Program #4: Java interview programming question on this keyword.

Zero argument constructor called.
Two argument constructor called.
x=1
y=2

Interview Programming questions on this keyword part 2

Baca selengkapnya

Selasa, 05 Juli 2016

Java Program to find shortest palindrome in string

Kris Kimcil 10.36 Komentar

We have a Letter or a word then we need add some letters to it and need to find out shortest palindrome
For example we take "S": S will be the shortest palindrome string.
If we take "xyz": zyxyz will be the shortest palindrome string
So we need to add some characters to the given string or character and find out what will be the shortest palindrome string by using simple java program.

Java example Program to find out shortest palindrome of given string

package shortestpalindromeexample.java;
import java.util.Scanner;
public class ShortestPalindromeDemo {
public static String shortestPalindrome(String str) {
int x=0;
int y=str.length()-1;
while(y>=0){
if(str.charAt(x)==str.charAt(y)){
x++;
}
y--;
}
if(x==str.length())
return str;
String suffix = str.substring(x);
String prefix = new StringBuilder(suffix).reverse().toString();
String mid = shortestPalindrome(str.substring(0, x));
return prefix+mid+suffix;
}
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.println("Enter a String to find out shortest palindrome");
String str=in.nextLine();
System.out.println("Shortest palindrome of "+str+" is "+shortestPalindrome(str));
}
}

Output:

Enter a String to find out shortest palindrome
java
Shortest palindrome of java is avajava

find shortest palindrome in java program

Baca selengkapnya

Minggu, 19 Juni 2016

Javascript interview questions

Validate email address using javascript

Kris Kimcil 05.52 Komentar

One of the famous interview question in JavaScript : how to validate email address in JavaScript.
In order to validate a text field of HTML we need a JavaScript function.
On submit form we need to call a java script function to validate all fields in the form also known as client side validation.
Now on form submit we need to check email text field and validate it whether entered email is in correct format or not for ex: instanceofjava@gmail.com.

JavaScript program for email validation:

<!DOCTYPE html>
<html>
<head>
<script>
function validateEmailForm() {
var x = document.forms["Form_Name"]["txt_email"].value;
var atpos = x.indexOf("@");
var dotpos = x.lastIndexOf(".");
if (atpos<1 || dotpos<atpos+2 || dotpos+2>=x.length) {
alert("Not a valid e-mail address");
return false;
}
}
</script>
</head>
<body>
<form name="Form_Name" action="User_email_validation.jsp" onsubmit="return
validateEmailForm();" method="post">
Email: <input type="text" name="txt_email">
<input type="submit" value="Submit">
</form>
</body>
</html>

Validate email in java-script using regular expression: on submit form validation

<!DOCTYPE html>
<html>
<head>
<script>
function validateEmailForm() {
var email = document.forms["Form_Name"]["txt_email"].value;
var re = /\S+@\S+\.\S+/;
return re.test(email);
}
}
</script>
</head>
<body>
<form name="Form_Name" action="User_email_validation.jsp" onsubmit="return
validateEmailForm();" method="post">
Email: <input type="text" name="txt_email">
<input type="submit" value="Submit">
</form>
</body>
</html>

HTML 5 Email validation:

<form>
<input type="email" placeholder="Enter your email">
<input type="submit" value="Submit">
</form>

email address validation code in java script

Baca selengkapnya

Core java Interview Questions

Java XML parsing using DOM parser

Kris Kimcil 04.28 Komentar

Employees.xml:

Employee.java

package javaXMLParsing;
public class Employee {
String id;
String firstName;
String lastName;
String location;
@Override
public String toString() {
return firstName+" "+lastName+"("+id+")"+location;
}
}

Java Example program to parse XML using DOM parser:

DOMParserDemo.java

package javaXMLParsing;
import java.util.ArrayList;
import java.util.List;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
public class DOMParserDemo {
public static void main(String[] args) throws Exception {
//Create object of DOM Builder Factory class By using
//DocumentBuilderFactory.newInstance() method
DocumentBuilderFactory factoryobj =
DocumentBuilderFactory.newInstance();
//Create DOM Builder Object from DocumentBuilderFactory object
DocumentBuilder builder = factoryobj.newDocumentBuilder();
//Load the XML document and parse it
Document documentobj =
builder.parse(
ClassLoader.getSystemResourceAsStream("javaXMLParsing/Employee.xml"));
List<Employee> empList = new ArrayList<>();
//Iterating through the nodes and extracting the data.
NodeList nodeList = documentobj.getDocumentElement().getChildNodes();
for (int i = 0; i < nodeList.getLength(); i++) {
//We have encountered an <employee> tag.
Node node = nodeList.item(i);
if (node instanceof Element) {
Employee emp = new Employee();
emp.id = node.getAttributes().
getNamedItem("id").getNodeValue();
NodeList childNodes = node.getChildNodes();
for (int j = 0; j < childNodes.getLength(); j++) {
Node cNode = childNodes.item(j);
//Identifying the child tag of employee every employee .
if (cNode instanceof Element) {
String content = cNode.getLastChild().
getTextContent().trim();
switch (cNode.getNodeName()) {
case "firstName":
emp.firstName = content;
break;
case "lastName":
emp.lastName = content;
break;
case "location":
emp.location = content;
break;
}
}
}
empList.add(emp);
}
}
//Printing the Employee list by using for each loop.
for (Employee emp : empList) {
System.out.println(emp);
}
}
}

Output:

saidesh kilaru(001)Bangalore
ajay chanukya(002)Chicago
Vinod Gandrakoti(003)Hyderabad

Baca selengkapnya

Sabtu, 18 Juni 2016

Core java Interview Questions java Collections interview Questions

Difference between Collections and Collection in java with example program

Kris Kimcil 09.07 1 Komentar

Famous java interview question: difference between collections and collection in java
Major difference between Collection and Collections is Collection is an interface and Collections is a class.
Both are belongs to java.util package
Collection is base interface for list set and queue.
Collections is a class and it is called utility class.
Collections utility class contains some predefined methods so that we can use while working with Collection type of classes(treeset, arraylist, linkedlist etc.)
Collection is base interface for List , Set and Queue.

Collection vs Collections

public interface Collection<E>
extends Iterable<E>

public class Collections
extends Object

difference between collections and collection in java

Collections utility class contains static utility methods so that we can use those methods by using class name without creating object of Collections class object
Lest see some methods of Collections class.

addAll: public static <T> boolean addAll(Collection<? super T> c,T... elements)
reverseOrder: public static <T> Comparator<T> reverseOrder()
shuffle: public static void shuffle(List<?> list)
sort:public static <T extends Comparable<? super T>> void sort(List<T> list)

How to Relate Collection and Collections

ArrayList is a Collection type of class means it is implementing Collection interface internally
Now lets see a java example program to sort ArrayList of elements using Collections.sort() method.

public class ArrayList<E>
extends AbstractList<E>
implements List<E>, RandomAccess, Cloneable, Serializable

1.Basic Java example program to sort arraylist of integers using Collections.sort() method

package com.javasortarraylistofobjects;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
public class SortArrayListExample{
public static void main(String[] args) {
//create an ArrayList object
ArrayList<Integer> arrayList = new ArrayList<Integer>();
//Add elements to Arraylist
arrayList.add(10);
arrayList.add(7);
arrayList.add(11);
arrayList.add(4);
arrayList.add(9);
arrayList.add(6);
arrayList.add(2);
arrayList.add(8);
arrayList.add(5);
arrayList.add(1);
System.out.println("Before sorting ArrayList ...");
Iterator itr=arrayList.iterator();
while (itr.hasNext()) {
System.out.println(itr.next());
}
/*
To sort an ArrayList object, use Collection.sort method. This is a
static method. It sorts an ArrayList object's elements into ascending order.
*/
Collections.sort(arrayList);
System.out.println("After sorting ArrayList ...");
Iterator itr1=arrayList.iterator();
while (itr1.hasNext()) {
System.out.println(itr1.next());
}
}
}

Output:

Before sorting ArrayList ...
10
7
11
4
9
6
2
8
5
1
After sorting ArrayList ...
1
2
4
5
6
7
8
9
10
11

Baca selengkapnya

Basic Java Example programs Core java Interview Questions

Java Program to find missing numbers in an array

Kris Kimcil 07.54 Komentar

To find missing numbers in an array first we need to make sure that array is sorted.
After sorting we need to check that array each element with next element then we can find the difference.
if Array is not sorted :To sort array use Arrays.sort(array);
If difference is 1 then no need to do any thing because numbers are in order.
If difference is not equal to 1 then we need to print all those numbers or pick those numbers and place it in one array.
this would be the logic to find missing numbers in an array
Here there may be a chance of array not starts with 1 then we need to check first itself whether array starts with 1 or not if not we need to print 1 to starting element of array.
for example int a[]={4,5,6,8}; then we need to print 1 2 3 7.

Lets see a java example program to find missing numbers in an array.

package arraysInterviewQuestions;
public class PrintMissingNumbers {
private static void findMissingNumber(int[] number){
// take max length as last number in array
int k[] = new int[number[number.length-1]];
int m=0;
if(number[0]!=1){
for (int x = 1; x < number[0]; x++) {
k[m] = x;
m++;
}
}
for (int i = 0; i < number.length -1; i++) {
int j = i+1;
int difference = number[j] - number[i] ;
if(difference != 1 ){
for (int x = 1; x < difference; x++) {
k[m] = number[i] + x;
m++;
}
}
}
System.out.println("missing numbers in array ::");
for (int l = 0; l < m ; l++) {
System.out.println( k[l]+" ");
}
}
public static void main(String[] args) {
int a[]= {2,4,6,9,10,20};
//if Array is not sorted :To sort array use Arrays.sort(a);
findMissingNumber(a);
}
}

program to find missing number in an array in java

Change the array in main method and practice try to find missing elements in an array that contains 1 to 100 numbers.

Baca selengkapnya

Jumat, 17 Juni 2016

Core java Interview Questions

Dynamic polymorphism in java with example program

Kris Kimcil 11.53 Komentar

Polymorphism means defining multiple methods with same name.

Two types of polymorphism
1.Static polymorphism
2.Dynamic polymorphism.

Static polymorphism:

Defining multiple methods with same name and with different type of arguments is known as static polymorphism.
We can achieve this static polymorphism using method overloading.

Static polymorphism in java with example program

package com.instanceofjava;
class A{
public void show(int a){
System.out.println("saidesh");
}
public void show(int a,int b){
System.out.println("ajay");
}
public void show(float a){
System.out.println("vinod");
}
public static void main(String args[]){
A a=new A();
a.show(10);
a.show(1,2);
a.show(1.2);
}
}

Output:

saidesh
ajay
vinod

Dynamic polymorphism:

Defining multiple methods with same name and with same signature in super class and sub class.
We can achieve dynamic polymorphism by using method overriding concept in java.
Define a method in super class and override same method with same signature in sub class
Whenever we call the method on t the object based on the object corresponding class method will be executed dynamically.

Java example program on dynamic polymorphism: (Real time example)

package MethodOverridingExamplePrograms;
public class Vehicle{
void Start(){
System.out.println("Vehicle started")
}
}

package MethodOverridingExamplePrograms;
public class Car extends Vehicle{
void Start(){
System.out.println("Car started")
}
}

package MethodOverridingExamplePrograms;
public class Bus extends Vehicle{
void Start(){
System.out.println("Bus started")
}
}

package MethodOverridingExamplePrograms;
public class Bike extends Vehicle{
void Start(){
System.out.println("Bike started")
}
}

package MethodOverridingExamplePrograms;
public class Test{
public static void startVehicle(Vehicle vh){
vh.start();
}
}

Dynamic polymorphism in java with example program

In the above example based on the object creation at run time corresponding class method will be executed.

Baca selengkapnya

Jumat, 10 Juni 2016

Core java Interview Questions java interview programs

toString() method in java with example program

Kris Kimcil 21.53 Komentar

toString() method belongs to object class.
By default it will be called once whenever we try to print object.
toString() method by default will print classname@hex representation of hashcode.
We can override this toString() method from object class.

public String toString(){
return null;
}

Advantage of toString() method in java.

When ever we try to print object by default toString() method will be called and print classname@HEX_hashcode.
We can represent object in String format using toString() method.
if we want to represent string representation of object then we need to override toString() method in our class and return values of the object as a String.

Java example program to print object without using toString() method.

Lets see an example program on printing object of a class.

package tostringexamples;
public class ToStringDemo {
int a,b;
ToStringDemo(int x, int y){
a=x;
b=y;
}
public static void main(String[] args) {
ToStringDemo obj= new ToStringDemo(1,2);
ToStringDemo obj2= new ToStringDemo(3,4);
System.out.println(obj);
System.out.println(obj2);
}
}

Output:

tostringexamples.ToStringDemo@2a139a55
tostringexamples.ToStringDemo@15db9742

In the above program when we print object of ToStringDemo class it prints ToStringDemo@2a139a55.
It means when ever we print object of the class toString() method will be called and by default toString() method print classname@HEX_hashcode.
To test this now we will override the toString() method and prints object of the class and if it calls our method then we can understand that when ever we print object by default toString() method will be called.

Java example program to print object by overriding toString() method.

override tostring method in java example

In above example when we print object it executed overridden toString() method.
By overriding toString() method we can represent object in string form.

toString() method used to convert data to String type.

By using toString method we can convert any wrapper object to string object

Java example program to convert integer to string using toString() method.

package tostringexamples;
public class ToStringDemo {
public static void main(String[] args) {
Integer a=12;
Integer b=37;
String str1=a.toString();
String str2 =b.toString();
System.out.println(str1);
System.out.println(str2);
}
}

Output:

Java example program to convert Float to String using toString() method.

package tostringexamples;
public class ToStringDemo {
public static void main(String[] args) {
Float a=12.0f;
Float b=33.4f;
String str1=a.toString();
String str2 =b.toString();
System.out.println(str1);
System.out.println(str2);
}
}

Output:

12.0
33.4

Baca selengkapnya

Sabtu, 28 Mei 2016

java technology Trending

Google Wins Java Copyright Case Against Oracle

Kris Kimcil 20.59 Komentar

Google has won a six-year court case brought by software firm Oracle, which claimed Google had infringed its copyright by using 11,500 lines of Java code in its Android operating system.
A jury has ruled that Google did not unfairly use parts of Java programming language.?Oracle? sought billions in damages from Google.
A judge on Thursday ruled Google's use of Java code in the Android operating system does not infringe on Oracle's copyrights and is protected by fair use. Oracle said it would appeal the decision.

Google Wins Java Copyright Case Against Oracle

Google wins $9bn Java copyright case with Oracle short by Swarnim Bagre / 05:49 pm on 27 May 2016,Friday
A federal jury in San Francisco ruled in favor of Google in the Java copyright case against Oracle on Thursday. Oracle had filed a suit in 2010 against Google claiming that it used code from the Oracle-owned Java programming language in Android without permission, seeking nearly $9 billion in damages. Oracle said that it will appeal against the decision
Copyright law expert Professor Pam Samuelson said the litigation was a "very unusual" fair use case, but that the jury ultimately agreed with the fair use defense, including the fact that "Google was the one who made an innovative and highly successful product from Java."
The sun has finally set on the Google and Oracle copyright battle. Google has won the long running Java lawsuit against Oracle as the jury found that Android OS does not violate copyrights owned by the latter.
Earlier in March Oracle demanded $9.3 billion in damages from Google over the use of Java API in Android which powers about 80% of the world’s mobile devices.. The company stated that Google needed a license to use its Java programming language to develop Android however, the jury rejected that argument and concluded Google made fair use of the code under copyright law. Oracle owns the programming language Java as it was acquired Sun Microsystems in 2010.

"Today's verdict that Android makes fair use of Java APIs represents a win for the Android ecosystem, for the Java programming community, and for software developers who rely on open and free programming languages to build innovative consumer products," Google said in an emailed statement.
The verdict is the latest development in the six-year legal skirmish over software copyrights with billions of dollars in damages at stake.
Oracle pledged it would appeal the verdict. "We strongly believe that Google developed Android by illegally copying core Java technology to rush into the mobile device market. Oracle brought this lawsuit to put a stop to Google’s illegal behavior. We believe there are numerous grounds for appeal," Oracle's general counsel Dorian Daley said in an emailed statement.

Baca selengkapnya

Kamis, 05 Mei 2016

linux unix commands

linux unix commands with examples

Kris Kimcil 08.35 Komentar

Unix/Linux Commands

Ls: List of all files

Syntax	Function
Ls-l	Complete properties of files or folders
Ls-lt	List of files or folders order by time
Ls-ltr	List of files or folders reverse order by time
Ls-d	Displays only directories

Cd: Change directory

Syntax	Function
cd-	Change directory to previous working directory
cd..	Change working directory to parent directory
Cd~	Same as above
cd../..	Change two levels up in the directory structure

Command	Syntax	Function
Cp(copy)	Cp source..destination	Copy the files and directories
sort	Sort[option][filename]	Sort the contents of text line by line
uniq	Uniq[option] filename	Eliminates duplicate lines from file
cat	Cat[options][files]	Display the contents of the file
join	Join[option]file1 file2	Join he two files based on key field present
sed	Sed..[script][input file]	Basic text transformations on input
head	head[option][files]	Prints first N lines from file
tail	Tail[option][file]	Print last N lines from file
alias	Alias[name=[’command]’]	Alternative name used for long strings
date	Date[option]…[format]	Print the date or change the system date and time
zip	Zip[option]zipfile file_list	Compress the file and reduce file size
grep	Grep[option]pattern[list of files]	Search the words in a file
find	Find[pathnames][condition]	Search for directories, files and links
cut	Cut[option]…[file]	Select sections of text from each line in a file
chmod	Chmod[option]mode… filename	Change or assign the permissions of files or directories
rmdir	Rmdir[options]directories	Remove directories
rm	Rm[options]directories/files	Remove both files and directories
mkdir	Mkdir[option]directories	Creates single or multiple directories
mv(move)	Mv[option]source.. destin	Move or rename the files and directories
hostname	Hostname[option][file]	Name of the system or server you are logged into.
paste	Paste[options]file-list	Merges the lines from multiple files
split	Split..filename	Split the one file in to many pieces
mail	Mail[options]to address [sending mail options]	Send email to users, also read delete mails
kill	Kill[-s signal] pid	Terminate or kill the process, also running the process
top	Top[options]	Provides system information
expr	Expr[expression]	For doing arithmetic operations
WC	Wc[options]filename	Finding number of lines, characters, words in a file
tr (Translate)	Tr[options]set1 [set2]	Translate, delete, squeezed characters