Find all palindrome strings in a java array.

In this article, we will see how to find all palindrome strings from an array. This is a very frequently asked questions in interview.  Also there is a question to find all palindrome number from an array.  Find few more collection interview question.  


PalindromeStrings.java

package com.javadevelopersguide.lab.basic;
/**
 * This program illustrates find all palindrome strings from array.
 *
 * @author manoj.bardhan
 *
 */
public class PalindromeStrings {
public static void main(String[] args) {
String stringArray[] = { "eye", "jdg", "javadevelopersguide", "aabaa", "hello", "pip" };
for (int i = 0; i < stringArray.length; i++) {
printOnlyPalindrom(stringArray[i]);
}
}
private static void printOnlyPalindrom(String str) {
String oldString = str;
StringBuilder builder = new StringBuilder(str);
if (builder.reverse().toString().equals(oldString)) {
System.out.println(oldString + " is a Palindrome.");
}
}
}

Output -

eye is a Palindrome String.
aabaa is a Palindrome String.
pip is a Palindrome String.

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Find More  :-

• Java 8 use Option - avoid NullPointerException
• Producer & Consumer problem solution using BlockingQueue.
• Write your first groovy program.
• Top 10 groovy interview question.
• Difference between groovy and java.
• What is full stack development experience.
• 5 fundamental questions of groovy.
• Write your first java program.
• Reverse string using recursive method in java.
• Comparator Interface with Examples
• Find the smallest value from array.

How to find duplicate elements from array in Java

In this article, we will see how to find the duplicate values from an array or list using java.  This is one of important programming questions in technical interview. Each interviewer has different approach to access the candidate. But, the logic and the approach by candidate is really matter. In this program we have used Map and List both, so its a kind of collections interview questions. You can find few more collection interview question.  Today we will see how to find the duplicate values from array. 

The logic is very simple here, see the below.

• At first we need we need to create a Map to hold the key-value pair. Where key is the array element and value is the counter for number of time the array element repeats.
• Then we will iterate the array and put into the map as per the above step. If the map contains the element earlier, then we will update the value +1.
• Finally we will have the map , which holds the array elements with the counter for repentance. 
• Now, we will iterate the Map , by checking the condition where the counter is more than 1 (i.e. its duplicated or repeated).

DuplicateFinder.java

package com.javadevelopersguide.lab.basic;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;
/**
 * This program illustrate to find the duplicate values in a List.
 *
 * @author manoj.bardhan
 *
 */
public class DuplicateFinder {
public static void main(String[] args) {
ArrayList<Integer> list = new ArrayList<Integer>(Arrays.asList(4, 3, 5, 25, 25, 25, 13, 5, 22, 4, 90));
System.out.println("List Date = " + list);
Map<Integer, Integer> map = new HashMap<Integer, Integer>();
for (int i = 0; i < list.size(); i++) {
if (map.isEmpty()) {
map.put(list.get(i), 1);
} else if (map.containsKey(list.get(i))) {
map.put(list.get(i), map.get(list.get(i)) + 1);
} else {
map.put(list.get(i), 1);
}
}
System.out.println("\nDuplicate values are: ");
// Iterate the Map and display the duplicate values.
for (Entry<Integer, Integer> entry : map.entrySet()) {
if (entry.getValue() > 1) {
System.out.println(entry.getKey());
// TODO We can now put these values into any list.
}
}
}
}

Output - 

Input List Data = [4, 3, 5, 25, 25, 25, 13, 5, 22, 4, 90]
Duplicate values are:
4
5
25

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Find More  :-

• Java 8 use Option - avoid NullPointerException
• Producer & Consumer problem solution using BlockingQueue.
• Write your first groovy program.
• Top 10 groovy interview question.
• Difference between groovy and java.
• What is full stack development experience.
• 5 fundamental questions of groovy.
• Write your first java program.
• Reverse string using recursive method in java.
• Comparator Interface with Examples
• Find the smallest value from array.
• Find the duplicate Strings and counts in a List.

Write a program to sort the employee by name, age using JDK 8

This program for writing a program to sort the employee by name and age using JDK 8. Java 8 introduced many out of box features for developers. The comparator in java 8 is marked as @FunctionalInterface, and it provide a cleaner way to develop your code. We had already discussed how the Comparator<T> interface works before java 8. In this post, we will use the stream api with comparator. 

Employee.java

package com.javadevelopersguide.lab.basic;
/**
 * @author manoj.bardhan
 *
 */
public class Employee {
private String name;
private int age;
private String department;
public Employee(String name, int age, String department) {
super();
this.name = name;
this.age = age;
this.department = department;
}
@Override
public String toString() {
return "\n Employee [name=" + name + ", age=" + age + ", department=" + department + "]";
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getDepartment() {
return department;
}
public void setDepartment(String department) {
this.department = department;
}
}

Now we will create an action or main method to use the above POJA class for sorting.

SortEmployeeWithStream.java

package com.javadevelopersguide.lab.basic;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.stream.Collectors;
/**
 * This program illustrates sort custom fields using JDK 8 (Stream & Comparator)
 *
 * @author manoj.bardhan
 *
 */
public class SortEmployeeWithStream {
public static void main(String[] args) {
Employee1 e1 = new Employee1("Ander Koli", 32, "Sales");
Employee1 e2 = new Employee1("Andrew Smith", 23, "Sales");
Employee1 e3 = new Employee1("David Jone", 52, "Sales");
Employee1 e4 = new Employee1("Cuba Station", 23, "Marketing");
Employee1 e5 = new Employee1("Bradley Head", 23, "Marketing");
Employee1 e6 = new Employee1("Peter Parker", 34, "Sales");
// Create an arraylist and add all the employee object into that list.
ArrayList<Employee1> employeeList = new ArrayList<Employee1>();
employeeList.add(e1);
employeeList.add(e2);
employeeList.add(e3);
employeeList.add(e4);
employeeList.add(e5);
employeeList.add(e6);
System.out.println("Employee list before sorting -\n" + employeeList);
ArrayList<Employee1> sortedList = (ArrayList) employeeList.stream()
.sorted(Comparator.comparing(Employee1::getName).thenComparing(Employee1::getAge))
.collect(Collectors.toList());
System.out.println("Employee list after sorting -\n" + sortedList);
}
}

Output-

Employee list before sorting -
[
 Employee1 [name=Ander Koli, age=32, department=Sales],
 Employee1 [name=Andrew Smith, age=23, department=Sales],
 Employee1 [name=David Jone, age=52, department=Sales],
 Employee1 [name=Cuba Station, age=23, department=Marketing],
 Employee1 [name=Bradley Head, age=23, department=Marketing],
 Employee1 [name=Peter Parker, age=34, department=Sales]]
Employee list after sorting -
[
 Employee1 [name=Ander Koli, age=32, department=Sales],
 Employee1 [name=Andrew Smith, age=23, department=Sales],
 Employee1 [name=Bradley Head, age=23, department=Marketing],
 Employee1 [name=Cuba Station, age=23, department=Marketing],
 Employee1 [name=David Jone, age=52, department=Sales],
 Employee1 [name=Peter Parker, age=34, department=Sales]]

The Comparator.comparing  and thenComparing  two static methods inside Comparator. As we know Comparator is a Functional interface which provides default and static methods along with implementation.  These functional interfaces are giving out of box functionality. See how before java 8 with Comparator interface examples.

Also we can achieve the above sorting by creating multiple different comparators , which we can use when we need. 

We have created two comparator as compareByAge, CompareByDept . Now we can use those comparators at any place we need along with stream. Below sample code snippet shows the usages. Read these reference documents for more about  stream, comparator, functions, jdk 8 features.

Comparator<Employee1> compareByAge = Comparator.comparing(Employee1::getAge);
Comparator<Employee1> compareByDept = Comparator.comparing(Employee1::getDepartment);
ArrayList<Employee1> sortedList = (ArrayList) employeeList.stream()
.sorted(compareByAge.thenComparing(compareByDept)).collect(Collectors.toList());

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Find More  :-

• Java 8 use Option - avoid NullPointerException
• Producer & Consumer problem solution using BlockingQueue.
• Write your first groovy program.
• Top 10 groovy interview question.
• Difference between groovy and java.
• What is full stack development experience.
• 5 fundamental questions of groovy.
• Write your first java program.
• Reverse string using recursive method in java.
• Comparator Interface with Examples.
• Find the smallest number in an array.

Java Comparator Example for custom sorting by employee age and department

This program illustrates , how to sort custom object using Comparator<T>. We have used Employee list to sort by age and department. As per the default ordering it will follow the natural ordering.

The below Employee class is our POJO , we will use this class to sort the employee list by age and department.

Employee.java

package com.javadevelopersguide.lab.basic;
/**
 * @author manoj.bardhan
 *
 */
public class Employee {
private String name;
private int age;
private String department;
public Employee(String name, int age, String department) {
super();
this.name = name;
this.age = age;
this.department = department;
}
@Override
public String toString() {
return "\n Employee [name=" + name + ", age=" + age + ", department=" + department + "]";
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getDepartment() {
return department;
}
public void setDepartment(String department) {
this.department = department;
}
}

Now, we need to create a comparator to compare two same objects. We can create as many comparators by implementing each field/attributes of the POJO. Its purely business requirement, how you need your sorting functionality. Here we need the sorting based on the employee  age and employee department.

EmployeeAgeComparator.java

package com.javadevelopersguide.lab.basic;
import java.util.Comparator;
/**
 * EmployeeAgeComparator is a comparator by Age.
 *
 * @author manoj.bardhan
 *
 */
public class EmployeeAgeComparator implements Comparator<Employee> {
@Override
public int compare(Employee emp1, Employee emp2) {
return emp1.getAge() - emp2.getAge();
}
}

EmployeeDeptComparator.java

package com.javadevelopersguide.lab.basic;
import java.util.Comparator;
/**
 * EmployeeDeptComparator is comparator by department.
 *
 * @author manoj.bardhan
 *
 */
public class EmployeeDeptComparator implements Comparator<Employee> {
@Override
public int compare(Employee emp1, Employee emp2) {
// Internally for comparing String we need to use compareTo()
return emp1.getDepartment().compareTo(emp2.getDepartment());
}
}

In the above we created two comparator for age and department. Now, we need to action on our comparators. We will call our newly created comparator from main() and see the result. Below EmployeeComparatorExample class show the comparator in action.

EmployeeComparatorExample.java

package com.javadevelopersguide.lab.basic;
import java.util.ArrayList;
import java.util.Collections;
/**
 * This program illustrates the simple use of Comparator<t> interface.
 *
 * @author manoj.bardhan
 *
 */
public class EmployeeComparatorExample {
public static void main(String[] args) {
Employee e1 = new Employee("Matt Kuban", 32, "IT");
Employee e2 = new Employee("Andrew Smith", 42, "HR");
Employee e3 = new Employee("Butler Jason", 52, "HR");
Employee e4 = new Employee("Miss Linda", 35, "HR");
Employee e5 = new Employee("Bradley Head", 23, "IT");
Employee e6 = new Employee("Peter Parker", 34, "ADMIN");
// Create an arraylist and add all the employee object into that list.
ArrayList<Employee> employeeList = new ArrayList<Employee>();
employeeList.add(e1);
employeeList.add(e2);
employeeList.add(e3);
employeeList.add(e4);
employeeList.add(e5);
employeeList.add(e6);
System.out.println("Employee Before Sort ::" + employeeList);
// Using EmployeeAgeComparator - to sort the employee by Age
EmployeeAgeComparator ageComparator = new EmployeeAgeComparator();
Collections.sort(employeeList, ageComparator);
// Using EmployeeDeptComparator - to sort the employee by Department
EmployeeDeptComparator deptComparator = new EmployeeDeptComparator();
Collections.sort(employeeList, deptComparator);
System.out.println("Employee After Sort ::" + employeeList);
}
}

Output :- 

Employee Before Sort ::[
 Employee [name=Matt Kuban, age=32, department=IT],
 Employee [name=Andrew Smith, age=42, department=HR],
 Employee [name=Butler Jason, age=52, department=HR],
 Employee [name=Miss Linda, age=35, department=HR],
 Employee [name=Bradley Head, age=23, department=IT],
 Employee [name=Peter Parker, age=34, department=ADMIN]]

Employee After Sort ::[
 Employee [name=Peter Parker, age=34, department=ADMIN],
 Employee [name=Miss Linda, age=35, department=HR],
 Employee [name=Andrew Smith, age=42, department=HR],
 Employee [name=Butler Jason, age=52, department=HR],
 Employee [name=Bradley Head, age=23, department=IT],
 Employee [name=Matt Kuban, age=32, department=IT]]

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Find More  :-

• Java 8 use Option - avoid NullPointerException
• Producer & Consumer problem solution using BlockingQueue.
• Write your first groovy program.
• Top 10 groovy interview question.
• Difference between groovy and java.
• What is full stack development experience.
• 5 fundamental questions of groovy.
• Write your first java program.
• Reverse string using recursive method in java.
• Comparator Interface with Examples.
• Java 8 Comparator::comparing examples.
• Find the smallest number in an array.

Comparator Interface with Examples

In this article we will see what is Comparable<T> interface ? How to use this interface with some sample examples ?

The Comparator interface is present inside java.util package. Its comparison function, which imposes a total ordering on some collection of objects. Its mostly used while sorting a collection of objects.  Means, it compares its two arguments for order.  Returns a negative integer,zero, or a positive integer as the first argument is less than, equal to, or greater than the second one.

The Comparators can be passed to a sort method (i.e. Collections.sort or Arrays.sort) to allow precise control over the sorting order. Comparators can also be used to control the order of certain data structures (such as sorted sets or sorted maps), or to provide an ordering for collections of objects that don't have a natural ordering.

This interface has one important method (Before JDK 8)  -

int compare(T o1, T o2);

The below Employee class is our POJO , we will use this class to sort the employee list by age and department.

Employee.java

package com.javadevelopersguide.lab.basic;
/**
 * @author manoj.bardhan
 *
 */
public class Employee {
private String name;
private int age;
private String department;
public Employee(String name, int age, String department) {
super();
this.name = name;
this.age = age;
this.department = department;
}
@Override
public String toString() {
return "\n Employee [name=" + name + ", age=" + age + ", department=" + department + "]";
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getDepartment() {
return department;
}
public void setDepartment(String department) {
this.department = department;
}
}

Now, we need to create a comparator to compare two same objects. We can create as many comparators by implementing each field/attributes of the pojo. Its purely business requirement, how you need your sorting functionality. Here we need the sorting based on the employee  age and employee department.

EmployeeAgeComparator.java

package com.javadevelopersguide.lab.basic;
import java.util.Comparator;
/**
 * EmployeeAgeComparator is a comparator by Age.
 *
 * @author manoj.bardhan
 *
 */
public class EmployeeAgeComparator implements Comparator<Employee> {
@Override
public int compare(Employee emp1, Employee emp2) {
return emp1.getAge() - emp2.getAge();
}
}

EmployeeDeptComparator.java

package com.javadevelopersguide.lab.basic;
import java.util.Comparator;
/**
 * EmployeeDeptComparator is comparator by department.
 *
 * @author manoj.bardhan
 *
 */
public class EmployeeDeptComparator implements Comparator<Employee> {
@Override
public int compare(Employee emp1, Employee emp2) {
// Internally for comparing String we need to use compareTo()
return emp1.getDepartment().compareTo(emp2.getDepartment());
}
}

In the above we created two comparator for age and department. Now, we need to action on our comparators. We will call our newly created comparator from main() and see the result. Below EmployeeComparatorExample class show the comparator in action.

EmployeeComparatorExample.java

package com.javadevelopersguide.lab.basic;
import java.util.ArrayList;
import java.util.Collections;
/**
 * This program illustrates the simple use of Comparator<t> interface.
 *
 * @author manoj.bardhan
 *
 */
public class EmployeeComparatorExample {
public static void main(String[] args) {
Employee e1 = new Employee("Matt Kuban", 32, "IT");
Employee e2 = new Employee("Andrew Smith", 42, "HR");
Employee e3 = new Employee("Butler Jason", 52, "HR");
Employee e4 = new Employee("Miss Linda", 35, "HR");
Employee e5 = new Employee("Bradley Head", 23, "IT");
Employee e6 = new Employee("Peter Parker", 34, "ADMIN");
// Create an arraylist and add all the employee object into that list.
ArrayList<Employee> employeeList = new ArrayList<Employee>();
employeeList.add(e1);
employeeList.add(e2);
employeeList.add(e3);
employeeList.add(e4);
employeeList.add(e5);
employeeList.add(e6);
System.out.println("Employee Before Sort ::" + employeeList);
// Using EmployeeAgeComparator - to sort the employee by Age
EmployeeAgeComparator ageComparator = new EmployeeAgeComparator();
Collections.sort(employeeList, ageComparator);
// Using EmployeeDeptComparator - to sort the employee by Department
EmployeeDeptComparator deptComparator = new EmployeeDeptComparator();
Collections.sort(employeeList, deptComparator);
System.out.println("Employee After Sort ::" + employeeList);
}
}

Output :- 

Employee Before Sort ::[
 Employee [name=Matt Kuban, age=32, department=IT],
 Employee [name=Andrew Smith, age=42, department=HR],
 Employee [name=Butler Jason, age=52, department=HR],
 Employee [name=Miss Linda, age=35, department=HR],
 Employee [name=Bradley Head, age=23, department=IT],
 Employee [name=Peter Parker, age=34, department=ADMIN]]

Employee After Sort ::[
 Employee [name=Peter Parker, age=34, department=ADMIN],
 Employee [name=Miss Linda, age=35, department=HR],
 Employee [name=Andrew Smith, age=42, department=HR],
 Employee [name=Butler Jason, age=52, department=HR],
 Employee [name=Bradley Head, age=23, department=IT],
 Employee [name=Matt Kuban, age=32, department=IT]]

JAVA 8 

In JDK 8,  Comparator<T> is functional Interface. Its annotated with @FunctionalInterface and this comparator interface has added few more default & static methods. As its a functional interface therefore its will be used as the assignment target for a lambda expression or method reference.

Below are few examples :-

default Comparator<T> reversed()
default Comparator<T> thenComparing(Comparator<? super T> other)
default <U> Comparator<T> thenComparing(
            Function<? super T, ? extends U> keyExtractor,
            Comparator<? super U> keyComparator)
default <U extends Comparable<? super U>> Comparator<T> thenComparing(
            Function<? super T, ? extends U> keyExtractor)
default Comparator<T> thenComparingInt(ToIntFunction<? super T> keyExtractor)

Here is the full list of methods added into Comparator<T> . We can use stream api of java 8 with lambda expression to implements comparator interface. We will see in the next subsequent posts on lambda expression and stream api.

Happy Learning.

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Find More  :-

• Java 8 use Option - avoid NullPointerException
• Producer & Consumer problem solution using BlockingQueue.
• Write your first groovy program.  
• Top 10 groovy interview question.
• Difference between groovy and java.
• What is full stack development experience. 
• 5 fundamental questions of groovy. 
• Write your first java program.
• Reverse string using recursive method in java.

Top 5 interview questions on BlockingQueue

1) What is BlockingQueue ? Under which package of JDK its available ?

Ans- A blocking queue is an interface. BlockingQueue implementations are thread-safe. It helps to handle multi threaded execution , specially its for producer and consumer problem.
The queue that blocks when you try to dequeue from it and the queue is empty, or if you try to enqueue items to it and the queue is already full. 

A thread trying to dequeue from an empty queue is blocked until some other thread inserts an item into the queue. 

There are few implementation for this BlockingQueue as below, all these classes available under java.util.concurrent package.

• ArrayBlockingQueue
• SyncronousBlockingQueue
• PriorityBlockingQueue
• LinkedBlockingQueue
• DelayQueue

2) What is the use of these methods peek(), poll(), take() and remove() ?

Ans - 
peek() :- This retrieves, but does not remove, the head of this queue,or returns null if this queue is empty. It doesn't throw any exception.

poll() :- This retrieves and removes the head of this queue,or returns null if this queue is empty.It doesn't throw any exception.

take() :- This retrieves and removes the head of this queue, waiting if necessary until an element becomes available. This method waits for certain time , if its interrupted then it throws InterruptedException. 

remove() :- This retrieves and removes the head of this queue. This method differs from poll() only in that it throws an exception (NoSuchElementException ) if this queue is empty.

Apart from the above difference take() method is provided by BlockingQueue i.e. java.util.concurrent.BlockingQueue.take(). Where as other methods provided by Queue i.e.  java.util.Queue.poll(), java.util.Queue.peek(), java.util.Queue.remove()


3) Is this possible to declare BlockingQueue implementation with ZERO/0 size?

Ans- Yes, if its unbounded implementation. But,if its bounded then we have to provide a capacity. The capacity must be greater than ZERO (i.e. capacity > 0).If we create a BlockingQueue with ZERO capacity then this will throw java.lang.IllegalArgumentException.


4) Write a program for demonstrating producer & consumer problem using blocking
 queue.

Ans- Find the answer here.


5) What is the difference between ArrayBlockingQueue and LinkedBlockingQueue ?

Ans- ArrayBlockingQueue is a bounded blocking queue backed by an array of objects. LinkedBlockingQueue is an optionally-bounded blocking queue based on linked nodes. 
Linked queues typically have higher throughput than array-based queues but less predictable performance in most concurrent applications.Linked nodes are dynamically 
created upon each insertion unless this would bring the queue capacity (Integer.MAX_VALUE). 



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Find More Questions & Answers Below.

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• Experienced Interview questions by Tavant Technologies.
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Top 10 spring boot interview questions for experienced

In this post, we will discuss some top 10 interview questions in spring boot. These questions are tricky and trending now-a-days job market. These interview questions might suitable for 0 to 8 years of experience.

1)  What is @SpringBootApplication does internally ?

Ans :- As per spring boot doc,  @SpringBootApplication annotation is equivalent to using @Configuration, @EnableAutoConfiguration, and @ComponentScan with their default attributes. Spring boot enable the developer to use single annotation instead of using multiple. But, as we know spring provided loosely coupled features we can use each individual annotation as per our project needs.

2)  How to exclude any package without using the basePackages filter?

Ans :-  There are many way you can filter any package. But, spring boot provides very tricky option to achieve this without touching the component scan. You can use "exclude" attribute, while using 

the annotation @SpringBootApplication. See the below code snippet.

@SpringBootApplication(exclude= {Employee.class})
public class FooAppConfiguration {}

3)  How to disable a specific auto-configuration class?

Ans :-  You can use "exclude" attribute of @EnableAutoConfiguration. If you find that specific auto-configuration classes that you do not want 

are being applied. 

//By using "exclude"

@EnableAutoConfiguration(exclude={DataSourceAutoConfiguration.class})

On the other way , if the class is not on the class path, you can use the "excludeName" attribute of the annotation and specify the fully qualified name instead.

//By using "excludeName"

@EnableAutoConfiguration(excludeName={Foo.class})

Also spring boot provides the facility to control the list of auto-configuration classes to exclude by using the spring.autoconfigure.exclude property. You can add into the application.properties. You can add multiple classes with comma separated.

//By using property filespring.autoconfigure.exclude=org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration

4)  What is Spring Actuator? What are its advantages?

Ans :-  This is one of the most common interview question in spring boot. As per spring doc definition, "an actuator is a manufacturing term that refers to a mechanical device for moving or controlling something. Actuators can generate a large amount of motion from a small change". 

As we know spring boot provides lots of auto-configuration features which helps the developer to develop ready for production components quickly.But, if you think what about the debugging , how to debug if something goes wrong. As a developer we always need analyze the logs and dig the data flow of our application to check whats going on. So, spring actuator provides a easy access to all those kind of features. It provides many features i.e. what are the beans created, what are the mapping in controller, what is the CPU usage, etc.Automatically auditing, health, and metrics gathering can be applied to your application.

It provides very easy way to access with few production ready REST endpoints to fetch all these kind of information from web. By, using these endpoints you do many things see here the endpoint docs. Nothing to worry about security, if Spring Security is present then these endpoints are secured by default using Spring Security’s content-negotiation strategy. Else , we can configure custom security by the help of RequestMatcher.

5)  How to enable/disable the Actuator ? 

Ans :-  Enabling/Disabling the actuator is easy, the simplest way to enable the features is to add  the dependency to the spring-boot-starter-actuator i.e. Starter. If you don't want the actuator to be enable, then don't add the dependency.

Maven dependency - 

<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
</dependencies>

Gradle dependency-

dependencies {
compile("org.springframework.boot:spring-boot-starter-actuator")
}

6)  What is Spring Initializer?

Ans :-  This may not be a difficult question , but the interviewer always checks the subject knowledge of the candidate. Its quite often that you can't expect questions that you have prepared :). However, this is very common question asked frequently in near time.

Spring initializer is a web application , which generates spring boot project with just what you need to start quickly.As always we need a good skeleton of the project, it help you to create a project structure/skeleton properly. Initializer here.

7)  What is shutdown in actuator? 

Ans :-  Shutdown is an endpoint which allows the application to be gracefully shutdown. This feature is not enabled by default.You can enable this by using management.endpoint.shutdown.enabled=true in your application.properties file. But, be careful about this if you are using this.

8)  Is this possible to change the port of Embedded Tomcat server in Spring boot?

Ans :-  Yes, its possible to change the port. You can use the application.properties file to change the port. you need to mention "server.port" (i.e. server.port=8081). Make sure you have application.properties in your project class path, rest spring framework will take care. If you mention server.port=0 , then it will automatically assign any available port.

9)  Can we override or replace the Embedded Tomcat server in spring boot ?

Ans :-  Yes, we can replace the embedded tomcat with any other servers by using the Starter dependencies.

You can use spring-boot-starter-jetty or spring-boot-starter-undertow as dependency as per your project need.

10)  Can we disable the default web server in the spring boot application?

Ans :-  The major strong point in spring is to provide flexibility to build your application loosely coupled. Spring provides features to disable the web server in a quick configuration. 

Yes, we can use the application.properties to configure the web application type i.e. spring.main.web-application-type=none


Reference documents :-
       Spring endpoints,spring boot annotation, spring servers config

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