InstanceOfJava: java interview programs

java remove duplicates from string array

Posted by: Instanceofjava Posted date: January 26, 2023 / comment : 0 java interview programs

we can remove duplicates from a string array using a combination of a Set and an array. A Set is a collection that does not allow duplicate elements, so by adding the elements of the array to a Set, any duplicates will be automatically removed.

Here is an example of how to remove duplicates from a string array:

String[] array = {"a", "b", "c", "a", "d", "b"};

Set<String> set = new HashSet<>(Arrays.asList(array));

String[] uniqueArray = set.toArray(new String[set.size()]);

In this example, we first create a string array with duplicate values. We then create a new HashSet and pass the array to its constructor, which automatically removes any duplicates. We then use the toArray() method of the Set to convert it back to an array, which now only contains unique values.

It's important to note that the order of the elements in the array is not guaranteed to be preserved after removing duplicates using this method. If you want to maintain the order of the elements in the array, you can use a List or a LinkedHashSet instead of a HashSet.

Removing duplicates from a string array in Java can be achieved by converting the array to a Set, which automatically removes any duplicates, and then converting it back to an array. This method is efficient and easy to implement, and it can be used to remove duplicates from any type of array.

In Java 8, can use the Stream API to remove duplicates from a string array. The Stream API provides a functional and declarative way of processing collections of data, including arrays. Here is an example of how to use the Stream API to remove duplicates from a string array:

String[] array = {"a", "b", "c", "a", "d", "b"};

String[] uniqueArray = Arrays.stream(array)

.distinct()

.toArray(String[]::new);

In this example, we first create a string array with duplicate values. We then create a stream of the array using the Arrays.stream() method, and then use the distinct() method to remove the duplicates. Finally, we use the toArray() method to convert the stream back to an array, which now only contains unique values.

In summary, in Java 8, you can use the Stream API to remove duplicates from a string array by creating a stream of the array and using the distinct() method to remove the duplicates. This method is efficient and easy to implement, and it can be used to remove duplicates from any type of array, it's a functional and declarative way of processing collections of data.

in both cases, the order of the elements in the array is not guaranteed to be preserved after removing duplicates, if you want to maintain the order you can use a List or a LinkedHashSet instead of a HashSet or use the distinct() method.

Java 8 provides multiple ways to remove duplicates from a string array using the Stream API, you can use the distinct() method or a collection such as a Set to remove duplicates, both methods are efficient and easy to implement.

what happens when a constructor is defined for an interface?

Posted by: Instanceofjava Posted date: January 22, 2023 / comment : 0 java interview programs

Interfaces in Java do not have constructors. An interface is a blueprint for a class and it cannot be instantiated. An interface defines a set of methods and variables that a class must implement, but it does not contain any implementation for those methods.
Java does not allow constructors to be defined in an interface, because the purpose of an interface is to define a set of methods that can be implemented by a class, and not to provide an implementation for those methods. Constructors are used to initialize an object, but since an interface cannot be instantiated, there is no object to initialize.
If you try to define a constructor in an interface, the compiler will throw an error: "Interface methods cannot have a body."
However, you can have a default method in an interface, which is a method with a defined body, but it is not a constructor.
In summary, constructors are not allowed in interfaces, because interfaces are used to define a set of methods that can be implemented by a class, and not to provide an implementation for those methods.
In Java 8 and later versions, the concept of a default method has been introduced. A default method is a method that has a defined body and can be used to provide a default implementation for a method in an interface, but it's not a constructor.

If you try to define a constructor in an interface, it will result in a compilation error.
Interfaces in Java do not have constructors. An interface is a blueprint for a class and it cannot be instantiated. An interface defines a set of methods and variables that a class must implement, but it does not contain any implementation for those methods.
When the compiler encounters a constructor definition in an interface, it will throw an error because constructors are not allowed in interfaces. The error message will typically be similar to "Interface methods cannot have a body" or "Illegal combination of modifiers: 'constructor' and 'interface'".

How to print array in java

Posted by: Instanceofjava Posted date: January 21, 2023 / comment : 0 java interview programs

To print an array in Java, you can use a for loop to iterate through the array and print each element. Here is an example of how to print an array of integers:

Here is a simple program that explains how to print an array of integers in java

int[] myArray = {1, 2, 3, 4, 5};
for (int i = 0; i < myArray.length; i++) {
System.out.print(myArray[i] + " ");
}

This will print the following output: "1 2 3 4 5".

Alternatively: Arrays.toString(myArray) and directly print the array.

System.out.println(Arrays.toString(myArray));

This will also print the array in same format "1 2 3 4 5"

We can also use the enhanced for loop (also known as the "for-each" loop) to print an array in Java. This type of loop automatically iterates through each element in the array, making it more concise and easier to read than a traditional for loop:

for (int element : myArray) {
System.out.print(element + " ");
}

This will also print the same output as the previous example "1 2 3 4 5".

When printing arrays of other types, such as Strings or objects, we can use the same approach. For example, if you have an array of Strings, you can use the enhanced for loop to print each element:

This will print the following output: "Hello World".

It's worth noting that, the Arrays.toString() method will work for all types of arrays, including arrays of objects, it will call the toString() method of each element in the array.

In case of the custom class objects, you may need to override the toString() method of the class.

Another way to print an array in Java is to use the Arrays.deepToString() method if the array is a multi-dimensional array. This method is similar to Arrays.toString(), but it can handle multi-dimensional arrays and it will recursively call itself for each sub-array. Here's an example of how to use Arrays.deepToString() to print a 2D array:

int[][] my2DArray = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
System.out.println(Arrays.deepToString(my2DArray))

This will print the following output: "[[1, 2, 3], [4, 5, 6], [7, 8, 9]]".

we can also use the java.util.Arrays.stream() method to print an array in Java 8 and later versions. This method returns a stream of the array's elements, which can then be passed to various stream operations such as forEach(). Here's an example of how to use Arrays.stream() to print an array:

int[] myArray = {1, 2, 3, 4, 5};

Arrays.stream(myArray).forEach(System.out::print);

This will also print the same output as the previous examples "1 2 3 4 5".

It's worth noting that when you use the Arrays.stream() method to print an array, it does not add any spaces or newlines between the elements, unlike the for loop and enhanced for loop. If we want to add spaces or newlines, you can use the map() method to transform each element into a string, and then use the forEach() method to print each string.

Java enum constructor

Posted by: Instanceofjava Posted date: January 10, 2023 / comment : 0 java interview programs

In Java, an enumeration is a special kind of class that represents a fixed number of predefined values. The values are defined as enum constants, which are static and final fields of the enumeration.

When you define an enum, you can also define a constructor for it, which is called when each enum constant is created. The constructor is passed the values of the constant's fields and can use those values to initialize the constant.

Here's an example of an enumeration called Size with a constructor that takes a single String argument:

In this example, the Size enumeration has four constants: SMALL, MEDIUM, LARGE, and EXTRA_LARGE. Each constant has an associated abbreviation, which is passed to the constructor when the constant is created. The constructor sets the value of the abbreviation field to the passed-in value.

You can call the constructor explicitly or it will be called automatically when enum constants are created, so the following code:

Size s = Size.SMALL;

is equivalent to

Size s = new Size("S");

When you define constructors for your enum, it is a best practice to make them private. So that no other classes can create an instance of your Enum. This way you can only use the predefined values of the Enum and not create any new value on runtime.

Java program to check valid Balanced parentheses

Posted by: Instanceofjava Posted date: July 03, 2019 / comment : 0 java interview programs

Balanced parentheses:

A string which contains below characters in correct order.
"{}" "[]" "()"
We need to check whether given string has valid order of parenthesis order.
If the parenthesis characters are placed in order then we can say its valid parentheses or balanced parentheses.
If the parentheses characters are not in correct order or open and close then we can say it is not balanced or invalid parenthesis.
Program to check given string has a valid parenthesis or not.

#1: Java example program to check given string has valid parenthesis or not.

package instanceofjava;
import java.util.Stack;
public class BalancedParenthensies {
public static void main(String[] args) {
System.out.println(checkParenthensies("{(xxx,yyy)}"));
System.out.println(checkParenthensies("{)(acd,bcvfs}"));
System.out.println(checkParenthensies("{(xxx},yyy)"));
System.out.println(checkParenthensies("[(xxx),yyy]"));
}
public static boolean checkParenthensies(String str) {
Stack<Character> object = new Stack<Character>();
for(int i = 0; i < str.length(); i++) {
char ch = str.charAt(i);
if(ch == '[' || ch == '(' || ch == '{' ) {
object.push(ch);
} else if(ch == ']') {
if(object.isEmpty() || object.pop() != '[') {
return false;
}
} else if(ch == ')') {
if(object.isEmpty() || object.pop() != '(') {
return false;
}
} else if(ch == '}') {
if(object.isEmpty() || object.pop() != '{') {
return false;
}
}
}
return object.isEmpty();
}
}

Output:

true
false
false
true

Java 8 stream filter method example program

Posted by: Instanceofjava Posted date: February 03, 2018 / comment : 0 java Collections interview Questions , java interview programs , java8

We can use java 8 stream class filter method to filter the values from a list /map in java
By Using filter() and collect() methods of stream class we can achieve this.
Lets see an example program to filter value from list without using java 8 streams and with java 8 stream filter.

#1: Java Example program to filter . remove value from list without using java 8 stream

package com.instanceofjava.filtermethodjava8
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
/**
* @author www.Instanceofjava.com
* @category interview programs
*
* Description: Remove value from list without using java 8 stream filter method
*
*/
public class fillterListJava8{
private static List<String> filterList(List<String> fruits, String filter) {
List<String> result = new ArrayList<>();
for (String fruit : fruits) {
if (!filter.equals(fruit)) {
result.add(fruit);
}
}
return result;
}
public static void main(String[] args) {
List<String> fruits = Arrays.asList("apple", "banana", "lemon");
System.out.println("Before..");
for (String str : fruits) {
System.out.println(str);
}
List<String> result = filterList(fruits, "lemon");
System.out.println("After..");
for (String str : result) {
System.out.println(str);
}
}
}

Output:

Before..
apple
banana
lemon
After..
apple
banana

#2: Java Example program to filter . remove value from list using java 8 java.util.stream

package com.instanceofjava.java8;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;
/**
* @author www.Instanceofjava.com
* @category interview programs
*
* Description: Remove value from list using java 8 stream filter method
*
*/
public class filterMethodOfStream {
public static void main(String[] args) {
List<String> fruits = Arrays.asList("apple", "banana", "lemon");
String value="lemon";
List<String> result = fruits.stream()
.filter(line -> !value.equals(line))
.collect(Collectors.toList());
result.forEach(System.out::println);
for (String str : result) {
System.out.println(str);
}
}
}

Output:

How to remove html tags from string java

Posted by: Instanceofjava Posted date: February 03, 2018 / comment : 0 java interview programs , java string interview programs

If you want to remove html tags from a string in java you need to use regex.
Using java regex we can trim/remove html tags from given string.
Lets see a java example program on how can we remove html code or html tags from a string in java.
Input String : hello
output: hello

#1: Java Example program to remove html tags from a string

package com.instanceofjava.removehtmltags;
/**
* @author www.Instanceofjava.com
* @category interview programs
*
* Description: java convert html to plain text/ trim html code from string in java
*
*/
public class RemoveHtmlTags {
public static void main(String[] args) {
String htmlStr = "Java Program to remove html tags from a String";
System.out.println(htmlStr);
htmlStr = htmlStr.replaceAll("\\<.*?\\>", "");
System.out.println(htmlStr);
}
}

Output:

Java Program to remove html tags from a String
Java Program to remove html tags from a String

Java 8 foreach example program

Posted by: Instanceofjava Posted date: January 31, 2018 / comment : 0 Java 8 , java interview programs

Java 8 introduces for each loop.
before that lest see an example of how normal java for each loop.

#1: Java Example program which explain use of for each loop.

package com.instanceofjava.java8;
import java.util.HashMap;
import java.util.Map;
public class ForEachLoop {
/**
* @author www.Instanceofjava.com
* @category interview questions
*
* Description: java 8 for each loop
*
*/
public static void main(String[] args) {
Map<String, Integer> stumarks = new HashMap<>();
stumarks.put("Sai", 65);
stumarks.put("Vamshi", 65);
stumarks.put("Mahendar", 76);
stumarks.put("Muni", 87);
stumarks.put("Manohar", 90);
for (Map.Entry<String, Integer> entry : stumarks.entrySet()) {
System.out.println(entry.getKey() + " marks : " + entry.getValue());
}
}
}

Output:

Muni marks : 87
Vamshi marks : 65
Mahendar marks : 76
Sai marks : 65
Manohar marks : 90

#2: Java Example program which explains the use of for each loop in java 8

In the above program we used for each loop to get key value pairs of map.
Same thing will be done in java 8 by using stumarks.forEach((k,v)->System.out.println( k + " marks : " + v));

Java program to write a string to file using PrintWriter

Posted by: Instanceofjava Posted date: January 30, 2018 / comment : 0 Files , java interview programs

We can write a string to text file in java in various ways.
Using PrintWriter we can write or append a string to the text file.
Using println() method of PrintWriter we can save or write string to text file.
After completion of using PrintWriter you need to close it by calling close() method.
If you are using java 7 , by using try with resources we can implement it and closing will be taken care automatically.
Now we will see an example program on how to write or save a string / string variable to a text file using java 7.

#1: Java Example program to write or save string to file using PrintWriter and java 7 try with resources.

package com.instanceofjava.writetofile;
import java.io.FileNotFoundException;
import java.io.PrintWriter;
/**
*
* @author www.instanceofjava.com
* @category: java example program
*
* Description: Write a java example program to write string to files using PrintWriter
*
*/
public class WriteStringToFile {
public static void main(String[] args) {
String str="Write String to file";
try( PrintWriter out = new PrintWriter("data.txt") )
{
out.println( str );
}
catch (FileNotFoundException e)
{
e.printStackTrace()
}
}
}

Java read file line by line example program

Posted by: Instanceofjava Posted date: January 29, 2018 / comment : 0 Core java Interview Questions , java interview programs

Reading a text file line by line in java can be done by using java.io.BufferedReader .
Create a BufferedReader class by passing new FileReader(new File("filename")) object to it's constructor.
By using readLine() method of BufferedReader class we can read line by line text from a text file as Strings.
Lets see a java example program on hoe to read data from file line by line using BufferedReader class readLine() method.
Java read lines from text file example program.

#1: Java Example program to read file line by line

package com.instanceofjava.readfile;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
/** * *
@author www.instanceofjava.com
* @category: Interview Programs
* @description: How to read text file line by line in java example program
* */
public class ReadFile {
public static void main(String[] args) {
try {
File fileName = new File("E:\\data.txt");
FileReader fileReader = new FileReader(fileName);
BufferedReader bufferedreader = new BufferedReader(fileReader);
StringBuffer sb = new StringBuffer();
String strLine;
while ((strLine = bufferedreader.readLine()) != null) {
sb.append(strLine);
sb.append("\n");
}
fileReader.close();
System.out.println(sb.toString());
} catch (IOException e) {
e.printStackTrace();
}
}
}

Output:

java read file line by line example
java read file line by line java 8
java read lines from text file
example bufferedreader java example

#2: Java example program to read text file line by line using java 7 try with resource example

#3: Java example program to read text file line by line using java 8 example (Using stream)

package com.instanceofjava.readfile;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.stream.Stream;
/**
*
* @author www.instanceofjava.com
* @category: Interview Programs
* @description: How to read text file line by line in java example program using java 8 stream
*
*/
public class ReadFile {
public static void main(String[] args) throws IOException {
try (Stream<String> stream = Files.lines(Paths.get("E:\\data.txt")))
{
stream.forEach(System.out::println);
}
}
}

Convert to maven project in eclipse java

Posted by: Instanceofjava Posted date: January 26, 2018 / comment : 0 Core java Interview Questions , java interview programs

In order to convert any java project in to maven using eclipse we need to install m2e plugin.
Latest versions of eclipse are coming with this m2e plugin by default.
If not found this plugin we can install it by help->install->click on add and enter http://download.eclipse.org/technology/m2e/releases.
currently i am using eclipse oxygen version so it is having m2e plugin.
I have created a normal java project and i want to convert that into a maven project.
To convert any project in to maven right click on the project and ->configure->convert to maven project.
After that a window will be opened and you need to enter group id and artifact id and then click on finish.
convert to maven project eclipse luna / convert to maven project is not visible in eclipse /convert to maven project option not available in eclipse.

Right click on project and select configure-> convert to maven project.

Project will be converted to maven by creating pom.xml file.

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.or
/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.instanceofjava.maven</groupId>
<artifactId>MavenProject</artifactId>
<version>0.0.1-SNAPSHOT</version>
<build>
<sourceDirectory>src</sourceDirectory>
<plugins>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.7.0</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
</plugins>
</build>
</project>

Add dependencies to your pom.xml file

<properties>
<springVersion>5.0.3.RELEASE</springVersion>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>${springVersion}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>5.0.3.RELEASE</version>
</dependency>
</dependencies>

Print Pascals triangle using java program

Posted by: Instanceofjava Posted date: August 13, 2016 / comment : 0 java interview programs , java programming interview questions

Pascals triangle means arranging numbers in pascal triangle format.
First row starts with number 1.
Here is the pascal triangle with 8 rows.

The sum of all numbers in each row will be double the sum of all numbers in above row
The diagonals adjacent to the border diagonals of 1's contains natural numbers in order

Program #1: Java example program to print numbers in pascals triangle pattern.

package interviewprograms.instanceofjava;
import java.util.Scanner;
/*
* www.instanceofjava.com
*/
public class PasclasTriangleProgram {
public static void main(String args[]){
Scanner in = new Scanner(System.in);
System.out.println("Enter number of rows ");
int rows= in.nextInt();
for(int i =0;i<rows;i++) {
int number = 1;
System.out.format("%"+(rows-i)*2+"s","");
for(int j=0;j<=i;j++) {
System.out.format("%4d",number);
number = number * (i - j) / (j + 1);
}
System.out.println();
}
}
}

Output:

Enter number of rows
8
1
1 1
1 2 1
1 3 3 1
1 4 6 4 1
1 5 10 10 5 1
1 6 15 20 15 6 1
1 7 21 35 35 21 7 1

1.Pattern Programs in java Part-1

2.Pattern Programs in java Part-2

3.Pattern Programs in java Part-3

Finding Factorial of a Number in Java

Posted by: Instanceofjava Posted date: August 13, 2016 / comment : 0 java interview programs , java programming interview questions

One of the famous java interview program for freshers is finding factorial of a number using java program
Calculating the factorial of a number using java example program with recursion.

Factorial number means multiplication of all positive integer from one to that number.
n!=1*2*3.......*(n-1)*n.
Here ! represents factorial.
Two factorial: 2!= 2*1=2
Three factorial: 3!= 3*2*1=6.
Four factorial : 4!= 4*3*2*1=24.
Five factorial: 5!= 5*4*3*2*1=120.
Six factorial: 6!= 6*5*4*3*2*1=720
Seven factorial: 7!= 7*6*5*4*3*2*1=5040
Eight factorial: 8!= 8* 7*6*5*4*3*2*1=40320.

By using loops we can find factorial of given number.
Lets how can we find factorial of a number using java program without recursion.

Program #1: Java program to find factorial of a number using for loop

package interviewprograms.instanceofjava;
import java.util.Scanner;
public class FactiorialProgram {
public static void main(String args[]){
Scanner in = new Scanner(System.in);
System.out.println("Enter a number to find factorial");
int n= in.nextInt();
int fact=1;
for (int i = 1; i < n; i++) {
fact=fact*i;
}
System.out.println("Factorial of "+n+" is "+fact);
}
}

Output:

Enter a number to find factorial
5
Factorial of 5 is 120

Program #2: Java program to find factorial of a number using recursion.

package interviewprograms.instanceofjava;
import java.util.Scanner;
public class FactiorialProgram {
public static void main(String args[]){
Scanner in = new Scanner(System.in);
System.out.println("Enter a number to find factorial");
int n= in.nextInt();
int fact=1;
for (int i = 1; i < n; i++) {
fact=fact*i;
}
System.out.println("Factorial of "+n+" is "+fact);
}
}

Output:

Enter a number to find factorial
5
Factorial of 5 is 120

Program #3: Java program to find factorial of a number using recursion (Eclipse)

Setter and getter methods in java with example program

Posted by: Instanceofjava Posted date: August 09, 2016 / comment : 3 java interview programs , java programming interview questions

If we want to access variables inside a class we can access them using object. object.variable_name; and if we want to change the value of variable we will assign using object.variable_name=value;
By using constructor we can assign some values to the class variables whenever object is created but this is one time initialization.

To assign some value to variable directly assigning value or get value of variable using object is not recommended.
Actually we need to use methods to perform any task. And to assign and to get values of a object we have setter and getter methods concept in java.
Getter and setter methods are like normal methods in java. but to initialize new value and get the value of instance variables we will use use these methods that is the reason behind specialty of these methods
We can set as well as get value from variables so these are called setter and getter methods.
so declare variables as private to prevent from accessing directly using object of the class. and use get and set methods in java like
setXXX() and getXXX to assign values and access variables . SetXXX() and getXXX() here set and get are naming conventions to be used. where as XXX represent variable names.
If we observe this it is pure encapsulation in java.

Set Method / Setter method in java:

Purpose of Setter method is to set new value or assign new value to instance variable .

Method name should follow naming convention setVARIABLENAME().
It should accept some value as an argument. here method argument should be of type of variable.
It should have a statement to assign argument value to corresponding variable.
It does not have any return type. void should be the method return type.
In order to set some value to variable we need to call corresponding setter method by passing required value.

package settterandgettermethods;
public class SetAndGet {
private String name;
private int id;
public void setName(String name) {
this.name = name;
}
public void setId(int id) {
this.id = id;
}
}

Get method / Getter method in java:

Purpose of Getter method is to get the value of the instance variable.

Method name should follow naming convention getVARIABLENAME().
It should not have any arguments.
It should return corresponding variable value.
So return type must be of type of variable we are returning from the method.
In order to get the variable value we need to call corresponding getter method of variable.

package settterandgettermethods;
public class SetAndGet {
private String name;
private int id;
public String getName() {
return name;
}
public void setId(int id) {
this.id = id;
}
public static void main(String args[]){
SetAndGet obj = new SetAndGet();
String name =obj.getName();
}
}

Java program to get and set variable values without setter and getter methods

package settterandgettermethods;
public class SetAndGet {
private String name;
private int id;
public static void main(String args[]){
SetAndGet obj = new SetAndGet();
obj.name="setting some value";
obj.id=1;
System.out.println(obj.name);
System.out.println(obj.id);
}
}

Output:

setting some value
1

Java program to get and set variable values with setter and getter methods

package settterandgettermethods;
public class SetAndGet {
private String name;
private int id;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public static void main(String args[]){
SetAndGet obj = new SetAndGet();
obj.setName("java");
obj.setId(1);
System.out.println(obj.getName());
System.out.println(obj.getId());
}
}

Output:

java
1

Find top two maximum numbers in a array java

Posted by: Instanceofjava Posted date: August 06, 2016 / comment : 0 java interview programs , java programming interview questions

Hi Friends today we will discuss about how to find top two maximum numbers in an array using java program.
For this we have written separate function to perform logic
findTwoMaxNumbers method takes integer array as an argument
Initially take two variables to find top to numbers and assign to zero.
By using for each loop iterating array and compare current value with these values
If our value is less than current array value then assign current value to max1
And assign maxone to maxtwo because maxtwo should be second highest.
After completion of all iterations maxone will have top value and maxtwo will have second maximum value.
Print first maximum and second maximum values.
So from main method create array and pass to findTwoMaxNumbers(int [] ar).

Program #1: Java interview programs to practice: find top two maximum numbers in an array without recursion

package arraysInterviewPrograms.instanceofjava;
public class FindTopTwo {
public void findTwoMaxNumbers(int[] array){
int maxOne = 0;
int maxTwo = 0;
for(int i:array){
if(maxOne < i){
maxTwo = maxOne;
maxOne =i;
} else if(maxTwo < i){
maxTwo = i;
}
}
System.out.println("First Maximum Number: "+maxOne);
System.out.println("Second Maximum Number: "+maxTwo);
}
public static void main(String a[]){
int num[] = {4,23,67,1,76,1,98,13};
FindTopTwo obj = new FindTopTwo();
obj.findTwoMaxNumbers(num);
obj.findTwoMaxNumbers(new int[]{4,5,6,90,1});
}
}

Output:

First Maximum Number: 98
Second Maximum Number: 76
First Maximum Number: 90
Second Maximum Number: 6

Program #2:Java program to find top two maximum numbers in an array using eclipse IDE

Java program to remove vowels from string java

Posted by: Instanceofjava Posted date: July 17, 2016 / comment : 0 java interview programs , java programming interview questions

java program to remove vowels from a string
To remove vowels from a string we can use predefined method of string replaceAll()
By passing all vowels to the method replaceAll() with empty it will replaces all vowels with empty.
Check below topic for more programs on string
Java Experience interview programs on strings

Program #1: Java example program to remove all vowels from a String

package inheritanceInterviewPrograms;
public class RemoveVowels {
/**
* @www.instanceofjava.com
* @String interview programs asked in interviews
* @Remove vowels from a string in java
*/
public static void main(String[] args) {
String str = "RemoveVowels";
String resustr = str.replaceAll("[aeiouAEIOU]", "");
System.out.println(resustr);
}
}

Output:

RmvVwls

Program #2: Java example program to remove all vowels from a String by taking input from user

Java Program to find shortest palindrome in string

Posted by: Instanceofjava Posted date: July 05, 2016 / comment : 0 Basic Java Example programs , java interview programs

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

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

Basic java programs

Posted by: Instanceofjava Posted date: March 08, 2016 / comment : 0 Core java Interview Questions , java interview programs

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