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 Q1171. What is the difference between broken and unstable build ?Jenkins
Ans. Broken Build means as unsuccessful build whereas unstable build means build was created successfully but one of the Post Build report failed or could be a Test failure.

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   Like         Discuss         Correct / Improve     jenkins  build management

 Q1172. What is the upstream and downstream project in Build Systems ?Jenkins
Ans. Upstream project is a project whose successful build is required for executing the existing project build whereas Downstream project is the one that is waiting for the upstream project to build as it has the upstream project as dependency.

For example - X project has an upstream project y and downstream project Z. So It means X has dependency Y and is a dependency for Z.

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   Like         Discuss         Correct / Improve     jenkins  build management

 Q1173. What are Node / Slaves in Jenkins ?Jenkins
Ans. Slaves are computers that are set up to build projects for a master.

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   Like         Discuss         Correct / Improve     jenkins  build management system

 Q1174. Do all java classes need a main method?
Ans. No, Main method is the entry point into an application. An application usually contain multiple classes to perform a function.

Lets take an example of a House, House usually have only one external Door and you may have internal doors to move around within a house. Internal Doors are methods of classes whereas External Door is a special method called main method.

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   Like         Discuss         Correct / Improve     main method

 Q1175. Does default methods introduce multiple inheritance and the Diamond problem in Java 8 ?Core Java
Ans. Default methods results in multiple inheritance of behavior and not of state. In case we try to implement multiple interfaces with default method having same name and signature, and don't override it in implementation class, it will throw an error.

For example -

interface MyInterface {
public void default myMethod(){
}
}

interface MyInterface2 {
public void default myMethod(){
}
}

class MyClass implements MyInterface,MyInterface2 {
}

This code will compilation error "Duplicate Default Method"

if we specify the definition of myMethod() in myClass, compiler won't complain and there is no conflict and MyClass can use overridden definition. But if we don't override myMethod() in MyClass, Java would be in conflict as to what definition should be carried to MyClass and hence throws compilation error.

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   Like         Discuss         Correct / Improve     default methods  java 8  multiple inheritance  object oriented programming (oops)  oops concepts  diamond problem   interfaces

 Q1176. What is a publisher in Jenkins ?Jenkins
Ans. A publisher is part of build process that reports whether the build is stable or not. For example - Junit Test report publisher.

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   Like         Discuss         Correct / Improve     jenkins  build management

 Q1177. Why do we use a copy constructor ?
Ans. Copy Constructor is used for creating a duplicate of another object. Duplicate object will have the same state of the copied object but will have independent values in different memory locations. Copy Constructor can be useful to create duplicates of immutable objects as the Original cannot be tampered. Moreover It can be useful if base copies are required for individual requests in threading.

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   Like         Discuss         Correct / Improve     copy constructor  clone  cloning object   immutable  immutability  immutability

Frequently asked question in companies using Rest Web services.
 Q1178. Different between POST and PUT in Rest Rest
Ans. PUT requests are only meant to place the object as it is on server. For example - You want a file to be uploaded and then placed in a particular folder or you want an Employee object to be persisted in the table.

POST requests are also meant to transfer information from client to server but that information once received at the server is evaluated , modified or refactored before persisting.

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   Like         Discuss         Correct / Improve     Put vs Post   Rest     Asked in 5 Companies        frequent

 Q1179. Should a Database Update Request be a POST or PUT Request in RestRest
Ans. It should be a POST Request

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   Like         Discuss         Correct / Improve     Put vs Post   Rest     Asked in 1 Companies

 Q1180. Should a DB Insert Request be a POST or PUT request in RestRest
Ans. It depends on whether the request object is persisted as it is

or

its first dismantled, modified or refactored and then inserted into DB.

In first case, it should be a PUT request whereas in second case it should be a POST Request.

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   Like         Discuss         Correct / Improve     Put vs Post   Rest     Asked in 2 Companies      intermediate        frequent

 Q1181. Is it Necessary to send a POST request with the Payload or a body ?Web Service
Ans. No, we can also send an empty body with the POST Request.

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   Like         Discuss         Correct / Improve     Get Request   Rest        rare

 Q1182. Can I hit the Rest Post Request through a browser address bar if it's not expecting any payload / body ? Rest
Ans. No, even if there is no payload, you can't hit the POST request by typing it into browser address bar. You will need a client that can make a POST Request.

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   Like         Discuss         Correct / Improve     Post Request   Rest  Calling Rest service through browser        rare

 Q1183. What are the different ways in which information can be sent to server in web service call ?Web Service
Ans. 1. As Request Param
2. As Path Param
3. Part of Payload / Body in case of PUT and POST Request

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   Like         Discuss         Correct / Improve     web service   rest      basic        frequent

Rarely asked as it was introduced with Java 8.
 Q1184. What is the use of :: operator wef from Java 8 ?Core Java
Ans. We can refer to a function using this operator like System.out.println(intList.stream().reduce(Math::max).get());

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   Like         Discuss         Correct / Improve     :: operator   lambda expression  java 8

 Q1185. Can we declare the main method as private ?Core Java
Ans. Yes, compiler won't complain but at runtime it will give an error saying "Error: Main method not found in class". Even though we can use this method as any other private method, it cannot be invocate by executing the class.

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   Like         Discuss         Correct / Improve     main method   main method visibility      basic
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 Q1186. What is Hot Deployment ?Server
Ans. It is the ability to deploy changes on the fly without need to first build , deploy and then restart. All these functions happens on the fly as soon as the changes are made to the code.

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   Like         Discuss         Correct / Improve     hot deployment  deployment   container   application server  production support

 Q1187. Difference between Hot and Cold Deployment ?Server
Ans. Cold Deployment is a conventional deployment mechanism that follows the multi step process to deploy code changes to the running app i.e Build -> Deploy - Restart.

whereas

Hot Deployment is deployment changes on the fly without need to first build , deploy and then restart. All these functions happens on the fly as soon as the changes are made to the code.

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   Like         Discuss         Correct / Improve     Hot deployment  cold deployment  application server  production support

 Q1188. What is wrong with the following if statement ?

if(x==y && x.equals(y) {
}		Core Java
Ans. x==y means that both references have same type and are pointing to same memory location and hence would always mean that they have same value.

x.equals(y) is not required in this case.

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   Like         Discuss         Correct / Improve     if statement  control statements  == and equals  ==  .equals   code optimization
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 Q1189. What is wrong with the following if statement ?

if(x==y || x.equals(y) {
}		Core Java
Ans. if x==y turns out to be true x.equals(y) will be true too. If x.equals(y) could be true even if x==y is true or not.

So the only possible outcomes are

1 || 1 = 1
0 || 1 = 1
0 || 0 = 0

i.e the outcome of x.equals(y)

check for x==y is not required in this if statement.

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   Like         Discuss         Correct / Improve     if statement  control statements  == and equals  ==  .equals   code optimization
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 Q1190. Does it make sense to clone an object which is supposed to be immutable ?Design
Ans. It make sense only if we intend to modify either of the object and would like to preserve original state in other. Otherwise we can reuse the original object by making it singleton.

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   Like         Discuss         Correct / Improve     clone  clone objects  prototype design pattern   immutable  immutability  immutability  cloning

 Q1191. Does an ArrayList allow elements of different types ? If not, Why the following code works List list1 = new ArrayList<>(); list1.add(1); list1.add("1");Core Java
Ans. With Java 7 or Later. If you don't declare the list to be of specific type , it treats it as list of objects. int 1 is auto boxed to Integer and "1" is String and hence both are objects.

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   Like         Discuss         Correct / Improve     arraylist  list  collections

 Q1192. Are Strings objects in Java ?Core Java
Ans. Yes, everything except primitive types are objects in Java.

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   Like         Discuss         Correct / Improve     string

 Q1193. Can we access private members of the parent class ? i.e Are private members of the class visible in the derived class ?Core Java
Ans. No, If both Parent and Derived are outer classes.

public class Vehicle {
private static String manufacturingDate = "2016";
}

public class Car extends Vehicle{
public static void main(String args[]){
System.out.println(manufacturingDate); // error - The field Vehicle.manufacturingDate is not visible
}
}

Yes, If derived is the inner class of Parent.

public class Vehicle {
private static String manufacturingDate = "2016";
static public class Car extends Vehicle{
public static void main(String args[]){
System.out.println(manufacturingDate); // no problem
}
}
}

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   Like         Discuss         Correct / Improve     private members   private methods   private variables   inheritance  object oriented programming (oops)  oops concepts   members visibility   inner classes  nexted classes      basic        frequent

 Q1194. Do we need to implement all interface methods if a class is implementing it ?Core Java
Ans. Yes, a Class is supposed to define all abstract methods declared in the interface. With Java 8 , Interfaces can have default methods which need not be implemented by the implementing class.

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   Like         Discuss         Correct / Improve     interfaces

 Q1195. What is IdentityHashMap ?Core Java
Ans. IdentityHashMap is a class that implements AbstractMap and provides a data structure with Elements having Key Value pair, just like HashMap. It is similar to HashMap except that it uses reference equality when comparing elements.

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   Like         Discuss         Correct / Improve     IdentityHashMap  map  hashmap  collections

 Q1196. How and when the Buffer is cleared when using Buffered Writer Classes ?Core Java
Ans. Buffer is cleared in 2 circumstances, i.e 1. naturally when the buffer is filled and 2. explicitly when the method flush is called ( for flushing the residual )

Ideally we just need to call flush once at the end of file writing so that the residual content should be dumped to file.

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   Like         Discuss         Correct / Improve     BufferedWriter  Writer  PrintWriter  File io  flush  file handling

 Q1197. Where do we generally use comparable interface ?Core Java
Ans. Implementing Comparable interface means that the elements of the class are comparable i.e the class provides the implementation of compareTo method that would help comparing the elements.

This is usually required if we are planning to sort elements of a collection, If compareTo method is not defined , the sorting class / method could never understand a way to compare its elements in order to sort them.

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   Like         Discuss         Correct / Improve     comparable interface
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 Q1198. Difference between multiple and multi level inheritance ?Core Java
Ans. Multiple Inheritance refers to the concept of a class inheriting multiple classes. Example - Class C extends Class A ,Class B. This is not allowed in Java.

Multilevel Inheritance refers to the concept of Inheritance in a chain. Example - Class B extends Class A, Class C extends Class B. This is permitted in Java.

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   Like         Discuss         Correct / Improve     inheritance  object oriented programming (oops)  oops concepts   multiple inheritance  object oriented programming (oops)  oops concepts   multi level inheritance  object oriented programming (oops)  oops concepts      Basic        frequent

 Q1199. What is meant by size and index of a collection ?Core Java
Ans. As the name suggest size is the size of collection / data structure i.e number of elements or memory utilized by the collection.

Index is the position of an element in a collection or data structure.

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   Like         Discuss         Correct / Improve     collection  index of collection  size of collection      Basic

 Q1200. What is a classpath in Java ?Core Java
Ans. Classpath is the parameter for JVM to look for java classes ( .class files ) that are to be looad by class loader

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   Like         Discuss         Correct / Improve     classpath     Asked in 1 Companies      basic

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