Run Postman API remote or code or command line

POSTMAN is used to run the APIs generally.

What if we want to create a collection in postman and run it from some other code or command line or schedule to run the API.

Yes this is possible with POSTMAN and its free.

Reference for running API using newman from CLI


Reference to Run POSTMAN API by triggering it from web through any other source

Windows Tips and Tricks

Open Command Prompt from Windows run :

Use the below syntax to open command prompt directly of the location or directory

cmd /K "cd /d c:\location"

Frequently asked java interview question and answers

Q. What are all the Object class methods?
A. equals, hashCode,toString,clone,wait,notify,notifyAll,getClass,finalize

Q. When do you go for Interface and abstract class?
A. When there is a complex logic to be used across the application, then provide that logic as a concrete method and place inside a abstract class as it allows both concrete and abstract methods. To get 100% abstraction, use interfaces in the application

Q. Write a psudo java code to print 1 to 10 numbers in sequence with two multiple threads in which one is printing even numbers and another is printing odd nos?
A. class Thread1 implements Runnable{

 @Override
 public synchronized void run() {
  for(int i=0;i<10 args="" auto-generated="" block="" catch="" class="" code="" e.printstacktrace="" e="" even="" evenoddthreaddemo="" for="" i="" if="" implements="" int="" main="" notify="" nterruptedexception="" numbers="" odd="" public="" r1="" r2="" run="" runnable="" static="" synchronized="" system.out.println="" t1.start="" t1="new" t2.start="" t2="new" thread1="" thread2="" thread="" todo="" tring="" try="" verride="" void="" wait="">

Q. What are the types of Inner Classes?
A. Anonymous inner class

Q. How to create a thread and which is best and why?
A. Using Thread© and Runnable(I)- Runnable is best as java does not support multiple inheritance.

Q. What is checked and unchecked exception?
A. Exception thrown by compiler - checked exception; exceptions thrown at runtime- unchecked exceptions

Q. Write the code to insert an element in ArrayList?
A. list.add(index, object)

Q. Differences between Array and ArrayList?
A. Array is fixed in size and allows homogenious elements Whereas ArrayList is growable and allows hetrogenious elements.

Q. What is HashMap ?
A. allows key and value pairs or entries

Q. Explain the internal implementation of HashMap?
A. It uses LinkedList data structures; when duplicate key found, will be replaced with update key; equals and hashCode should be overridden when custom objects are used.

Q. What is thread executor framework?
A. Used to call all multiple thread tasks with only one thread

Q. What is Serialization?
A. Sending objects over network. Objects will be converted to streams.

Q. How to synchronize a class?
A. We can use 'synchronized' key word along with a method, used for a block

Q. What is garbage collection?
A. All objects with no references will be collected by garbage collector

Q. How to customize garbage collection in Java?
A. I think we cannot. JVM will take care of it.

Q. What is Generics in Java?
A. Provides Type safety and avoid external type Casting

Q. Features of Java 8?
A. Default/static method Interfaces, Functional Interfaces, Lamda Expressions, Java Stream API and etc

Q. When there is a requirement to do frequent insertions and deletions, which collection is useful and why?
A. LinkedList as it is node based data structure

Q. what is the code to write Immutable object?
A. Need to make the class as final, and all fields must be either private or final.

Q. How to sort objects in java?
A. Using Comparable and Comparator

Q. Write the code to sort using Comparable?
A.

class Person implements Comparable{
    private String empName;
    private Integer empId;
    public Person(Integer id,String name){
     this.empId = id;
     this.empName = name;
    }
  
   @Override
   public int compareTo(Person e){
     return (this.empId - e.empId);
   }
  
    public String toString(){
     return empId+" "+empName;
     } }
    public class ComparableDemo {
   public static void main(String[] args) {
    Person e1 = new Person(3,"XXX");
    Person e2 = new Person(1,"YYYY");
    Person e3 = new Person(2,"ZZZ");
  
    List empList = new ArrayList();
    empList.add(e1);
    empList.add(e2);
    empList.add(e3);
  
    Collections.sort(empList);
  
    for(Person e:empList)
     System.out.println(e);
    }}

Q. When will you get StackOverflow Exception?
A. When we create an object inside a loop without having end condition

Q. What is final, finally, finalize?
A. final - a class with final cannot be subclassed - a final method cannot be overridden - a final variable cannot be re-initialized; finally - code gets executed irrespective of an exception occurred, its gets executed always except when System.exist(0) is used. finalize() - used before objects get garbage collected.

Q. Differences between throw and throws?
A. throw should be used along with throws but not vice versa. When developer develops custom exception, throw is useful to throw that exception.

Q. What is concurrent Map in java?
A. ConcurrentHashMap is thread-safe that is the code can be accessed by single thread at a time .
while HashMap is not thread-safe .

Q. What are all the oops conecpts and explain?
A. overloading,overriding; Encapsulation-gives security to the code/fields; Abstraction-hides the complexity of the code and just gives the functionality

Q. Which design patterns do you know?
A. MVC, Singleton, Factory, VO, DTO, FrontEndController

Q. What is implict object in jsp?
A. Ready made objects which needs no instantiation

Q. What are all the implicit objects in jsp?
A. request,response,session,out,application,page,pageContext,exception,config

Q. How to establish a connection in jdbc?
A. load the driver class, get the connection, create statement, prepare the query, execute the query, get the resultset object, iterate it and get the results or executeUpdate for non-select queries

Q. What are the types of Statements?
A. Simple sTatement, PreparedStatement, CallableStatement

Q. What is PreparedStatement and what is the advantage of it?
A. PreparedStatement allows to enter the values using setter methods and query will be compiled and placed at server side only once.

Q. Did you work on tuning queries/tables in db?
A. indexing, using views

Q. What are ACID properties?
A. Automicity, Consistency, Isolation, Durabiltiy

Q. How to get data from multiple tables?
A. Using joins - inner join, out joins-left and right, full join

Q. What are all the Isolation levels?
A. Read-only, Read-write…

Q. Which version of Hibernate used in your project?
A. 3.x

Q. What is hibernate configuration file?
A. a xml file where db related stuff, beans, hibenate mapping file gets configured.

Q. What is alternative for hibernate configuration?
A. We can use Java related api.

Q. What are all the hibenate properties?
A. dialect to show db equivalent qeuries, show-sql , hbm2ddl,…

Q.What is hibernate?
A. its an ORM tool where we can map a java class object with record in a table

Q. What are all the associations available in hibernate?
A. one-to-one; one-to-many;many-to-one;many-to-many

Q. What oops concepts are used in hibernate?
A.inheritance and association

Q. What is inverse="true"/"false"?
A. true-birectional association; false-uni-directional association

Q. What are all the generators in hibernate?
A. generates ids - assigned, sequence, increment…

Q. What are all the classes/interfaces used in hibernate?
A. Configuration, SessionFactory, Session, Transaction

Q. What are the states of object in hibenate?
A. Transient, Persistant, Detached

Q. what is get() and load() in hibernate?
A. get()- loads a class and returns null when specific object was not found; load()- loads class and return ObjectNotFound exception when the specific object not found.

Q. When the objects are moved to persistant state?
A. after session.flush()

Q. What is connection pool?
A. a pool of connection/session objects available and used connection will be moved to this pool.

Q. What is the use of connection pool?
A. Developer can use readily available session in his code.

Q. What is the Spring MVC flow?
A. request --> DispatcherServlet -->HandlerMaaping -->Controller--returns ModelAndView object>ViewResolver-->View

Q. What is bean?
A. Any simple java class with setters and getters.

Q. What are all the modules in spring?
A. Spring core, Spring MVC. Knowledge on remianing modules like Spring JDBC, Spring ORM, Spring AOP

Q. What is IOC or Inversion of control?
A. Design pattern stands for Inversion Of Control. Dependency Injection in spring describes one of the implementation of it.

Q. What is AOP?
A. Stands Aspect Oriented Programming. Useful in separating the business logic from all others like logging, exception handling, tx management

Q. Did you work at authorization part of application?
A. Not get a chance but aware of it. In Spring , Spring Security module is there to do so.

Q. What are the events in spring?
A. ContextRefreshedEvent, ContextStartedEvent, ContextStoppedEvent, ContextClosedEvent, RequestHandledEvent

Q. How to configure mail properties in spring?
A. Used spring given bean called ProperyPlaceHolderConfigurer. Added the mail.properties to the classpath. And retrieved them and added to "JavaMailSenderImpl" using ${}

Q. Why do we use ApplicationContext instead BeanFactory in Spring?
A. ApplicationContext supports all advanced features like events, i18n.,…

Q. What is Criteria api in Spring?
A. Used to put constraints on entity using static classes like Expressions,…

Q. How to call procedures and functions?
A. Used directly as native sql query and retrieved the results

Q. Do you why industry is prefering REST ?
A. for high performance in terms of fast and easy implementation

Java OOPs Concepts

In this page, we will learn about basics of OOPs. Object Oriented Programming is a paradigm that provides many concepts such as inheritance, data binding, polymorphism etc.

Simula is considered as the first object-oriented programming language. The programming paradigm where everything is represented as an object, is known as truly object-oriented programming language.

Smalltalk is considered as the first truly object-oriented programming language.

OOPs (Object Oriented Programming System)

Object means a real word entity such as pen, chair, table etc. Object-Oriented Programming is a methodology or paradigm to design a program using classes and objects. It simplifies the software development and maintenance by providing some concepts:

• Object
• Class
• Inheritance
• Polymorphism
• Abstraction
• Encapsulation

Object

Any entity that has state and behavior is known as an object. For example: chair, pen, table, keyboard, bike etc. It can be physical and logical.

Class

Collection of objects is called class. It is a logical entity.

Inheritance

Class

When one object acquires all the properties and behaviours of parent object i.e. known as inheritance. It provides code reusability. It is used to achieve runtime polymorphism.

Polymorphism

When one task is performed by different ways i.e. known as polymorphism. For example: to convince the customer differently, to draw something e.g. shape or rectangle etc.

In java, we use method overloading and method overriding to achieve polymorphism.

Another example can be to speak something e.g. cat speaks meaw, dog barks woof etc.

Abstraction

Hiding internal details and showing functionality is known as abstraction. For example: phone call, we don't know the internal processing.

In java, we use abstract class and interface to achieve abstraction.

Encapsulation

Binding (or wrapping) code and data together into a single unit is known as encapsulation. For example: capsule, it is wrapped with different medicines.

A java class is the example of encapsulation. Java bean is the fully encapsulated class because all the data members are private here.

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Use the below URL for installing b2b accelerator .

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Difference between ArrayList and LinkedList in Java

ArrayList and LinkedList both implements List interface and their methods and results are almost identical. However there are few differences between them which make one better over another depending on the requirement.

ArrayList Vs LinkedList

1) Search: ArrayList search operation is pretty fast compared to the LinkedList search operation. get(int index) in ArrayList gives the performance of O(1) while LinkedList performance is O(n).

Reason: ArrayList maintains index based system for its elements as it uses array data structure implicitly which makes it faster for searching an element in the list. On the other side LinkedList implements doubly linked list which requires the traversal through all the elements for searching an element.

2) Deletion: LinkedList remove operation gives O(1) performance while ArrayList gives variable performance: O(n) in worst case (while removing first element) and O(1) in best case (While removing last element).

Conclusion: LinkedList element deletion is faster compared to ArrayList.

Reason: LinkedList’s each element maintains two pointers (addresses) which points to the both neighbor elements in the list. Hence removal only requires change in the pointer location in the two neighbor nodes (elements) of the node which is going to be removed. While In ArrayList all the elements need to be shifted to fill out the space created by removed element.

3) Inserts Performance: LinkedList add method gives O(1) performance while ArrayList gives O(n) in worst case. Reason is same as explained for remove.

4) Memory Overhead: ArrayList maintains indexes and element data while LinkedList maintains element data and two pointers for neighbor nodes hence the memory consumption is high in LinkedList comparatively.

There are few similarities between these classes which are as follows:

1. Both ArrayList and LinkedList are implementation of List interface.
2. They both maintain the elements insertion order which means while displaying ArrayList and LinkedList elements the result set would be having the same order in which the elements got inserted into the List.
3. Both these classes are non-synchronized and can be made synchronized explicitly by using Collections.synchronizedList method.
4. The iterator and listIterator returned by these classes are fail-fast (if list is structurally modified at any time after the iterator is created, in any way except through the iterator’s own remove or add methods, the iterator will throw a ConcurrentModificationException).

When to use LinkedList and when to use ArrayList?

1) As explained above the insert and remove operations give good performance (O(1)) in LinkedList compared to ArrayList(O(n)). Hence if there is a requirement of frequent addition and deletion in application then LinkedList is a best choice.

2) Search (get method) operations are fast in Arraylist (O(1)) but not in LinkedList (O(n)) so If there are less add and remove operations and more search operations requirement, ArrayList would be your best bet.

Difference Between String ,StringBuilder and StringBuffer

Difference Between String , StringBuilder and StringBuffer Classes with Example : Java

Today we are going to understand the difference between String , StringBuilder and StringBuffer . As you will find that there are minor differences between the above mentioned classes.

String

String is immutable  ( once created can not be changed )object  . The object created as a String is stored in the  Constant String Pool  .
Every immutable object in Java is thread safe ,that implies String is also thread safe . String can not be used by two threads simultaneously.
String  once assigned can not be changed.

String  demo = " hello " ;

// The above object is stored in constant string pool and its value can not be modified.

demo="Bye" ;     //new "Bye" string is created in constant pool and referenced by the demo variable           
 // "hello" string still exists in string constant pool and its value is not overrided but we lost reference to the  "hello"string 
StringBuffer

StringBuffer is mutable means one can change the value of the object . The object created through StringBuffer is stored in the heap . StringBuffer  has the same methods as the
StringBuilder , but each method in StringBuffer is synchronized that is StringBuffer is thread safe .

Due to this it does not allow  two threads to simultaneously access the
same method . Each method can be accessed by one thread at a time .

But being thread safe has disadvantages too as the performance of the
StringBuffer hits due to thread safe property . Thus  StringBuilder is
faster than the StringBuffer when calling the same methods of each
class.

StringBuffer value can be changed , it means it can be assigned to the new value . Nowadays its a most common interview question ,the differences between the above classes .

String Buffer can be converted to the string by using
toString() method.
StringBuffer demo1 = new StringBuffer("Hello") ;
// The above object stored in heap and its value can be changed .
demo1=new StringBuffer("Bye");
// Above statement is right as it modifies the value which is allowed in the StringBuffer
StringBuilder
StringBuilder  is same as the StringBuffer , that is it stores the object in heap and it can also be modified . The main difference between the StringBuffer and StringBuilder is that StringBuilder is also not thread safe. 
StringBuilder is fast as it is not thread safe . 

StringBuilder demo2= new StringBuilder("Hello");

// The above object too is stored in the heap and its value can be modified

demo2=new StringBuilder("Bye");

// Above statement is right as it modifies the value which is allowed in the StringBuilder

----------------------------------------------------------------------------------

                                    String                    StringBuffer         StringBuilder

----------------------------------------------------------------------------------                

Storage Area | Constant String Pool           Heap                       Heap

Modifiable     |  No (immutable)            Yes( mutable )          Yes( mutable )

Thread Safe   |           Yes                                  Yes                              No

 Performance |         Fast                                Very slow                    Fast

-----------------------------------------------------------------------------------