InstanceOfJava

Java Program to find missing numbers in an array

Posted by: Instanceofjava Posted date: June 18, 2016 / comment : 0 Basic Java Example programs , Core java Interview Questions

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.

Dynamic polymorphism in java with example program

Posted by: Instanceofjava Posted date: June 18, 2016 / comment : 0 Core java Interview Questions

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.

toString() method in java with example program

Posted by: Instanceofjava Posted date: June 11, 2016 / comment : 0 Core java Interview Questions , java interview programs

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

Google Wins Java Copyright Case Against Oracle

Posted by: Instanceofjava Posted date: May 29, 2016 / comment : 0 java , technology , Trending

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.

linux unix commands with examples

Posted by: Instanceofjava Posted date: May 05, 2016 / comment : 0 linux unix commands

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

How to get table cell data using JavaScript

Posted by: Instanceofjava Posted date: May 02, 2016 / comment : 0 Javascript interview questions

How to get table row data in javascript:

When we are working with HTML tables we will get a scenario like to get whole table rows data, or table td values , table cell value in JavaScript.
For that we need to read the table by using JavaScript.
lets see example on get table cell data using java script.
Before that lets see how to read the data of table using JavaScript
To find number of rows of a table by using table id in JavaScript.

var numberOfrows=document.getElementById("tableData").rows.length;

Get number of cells or number of tds inside each tr (table row)

var numberoftds = document.getElementById("tableData").rows[0].cells.length;

JavaScript get table row values get table td data

var numberoftds = document.getElementById("tableData").rows[0].cells.item(0).innerHTML;

Example on get table each row data using javascript:

<script type="text/javascript">
function checkFun() {
var n1 = document.getElementById("tableData").rows.length;
var i=0,j=0;
var str="";
for(i=0; i<n1;i++){
var n2 = document.getElementById("tableData").rows[i].cells.length;
for(j=0; j<n2;j++){
var x=document.getElementById("tableData").rows[i].cells.item(j).innerHTML;\
str=str+x+":";
}
str=str+"#";
}
document.getElementById("tablecontent").innerHTML=str;
}
</script>

<body onload="checkFun()">
<table id="tableData" border="1">
<tr>
<td >37</td>
<td >46</td>
<td >3</td>
<td >64</td>
</tr>
<tr>
<td >10</td>
<td >4</td>
<td >7</td>
<td >21</td>
</tr>
</table>
<p id="tablecontent" ></p>
</body>

get table cell row td data value javascript

Here in this example on page loading we called the JavaScript function
For that used body onload="func()" .
Practice this example in your System.

Control statements in java with examples

Posted by: Instanceofjava Posted date: April 29, 2016 / comment : 0 Core java Interview Questions

Programs in java will be executed in sequential manner means line by line execution of statements.
By using control statements we can control the flow of execution.
We have three types of control statements in java.

Decision making Statements.
Iteration statements.
Branching statements.

1.Decision making statements in java:

In some cases we will have a situation like need to execution set of statements based on a condition
In this scenario we need to use decision making statements in java.

if
if-else
if-else-if
switch

Simple if

Based on some condition if we want to execute some set of statements then we need to use if condition in java.
We need to keep all the required statements inside if block .
If the condition is true then control executes the whole block otherwise it skips the if block of statements.

if( condition ){
// code
}

Java example program on if control statement:

package controlstatementsinjava;
import java.util.Scanner;
public class ControlStatementsInjava {
/**
* @website: www.instanceofjava.com
*/
public static void main(String[] args) {
Scanner in= new Scanner(System.in);
System.out.println("Please enter a number");
int n=in.nextInt();
if(n%2==0){
System.out.println(n+" is even number");
}
if(n%2!=0){
System.out.println(n+" is odd number");
}
}
}

Output:

Please enter a number
5
5 is odd number

If else condition:

If the condition is true then control executes the whole block otherwise it skips the if block of statements
if condition is false if we need to execute another set of statement we can write another if and keep all the statements in that block.
instead of checking multiple times we can simply use else block .
More about in else statement in java

if( condition ){
// code
}else{
//code
}

if else control statement with example programs:

package controlstatementsinjava;
import java.util.Scanner;
public class ControlStatementsInjava {
/**
* @website: www.instanceofjava.com
*/
public static void main(String[] args) {
Scanner in= new Scanner(System.in);
System.out.println("Please enter a number");
int n=in.nextInt();
if(n%2==0){
System.out.println(n+" is even number");
}else{
System.out.println(n+" is odd number");
}
}
}

Output:

Please enter a number
5
5 is odd number

if else ladder :

In some cases we may get requirement with multiple conditions in such cases we need to use if else ladder.(if -else-if-else if -else...)

if( condition ){
// code
}else if{
//code
}else {
//code
}

if else if control statement with example programs:

package controlstatementsinjava;
import java.util.Scanner;
public class ControlStatementsInjava {
/**
* @website: www.instanceofjava.com
*/
public static void main(String[] args) {
Scanner in= new Scanner(System.in);
System.out.println("Please enter your age");
int age=in.nextInt();
if(age<=18){
System.out.println("Your age is between 1-18");
}else if ((age>=18) && (age<=35)){
System.out.println(" Your age is between 18-35");
}
else if ((age>=35) && (age<=50)){
System.out.println(" Your age is between 35-50");
}else{
System.out.println(" Your age is above 50");
}
}
}

Output:

Please enter your age
20
Your age is between 18-35

Switch statement in java:

Instead if writing number of if conditions we can use single switch statement

switch(value)
case n1: statements;
break;
case n2 : statements;
break;
default: statements;
}

Java example program on switch statement in java:

Subscribe to: Posts ( Atom )