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Q1981. Write a program to sort a stack in ascending order You should not make any assumptions about how the stack is implemented The following are the only functions that should be used to write this program: push | pop | peek | isEmpty

Algorithm

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Q1982. How can we convert String into Char array and vice versa ?

Core Java

Ans. There is a method toCharArray() within String class that can be used to convert string to char array.

string.toCharArray();

String class has an argument constructor that takes a char array and create a string

new String(charArray);

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Q1983. How can we convert a character or a character array into a String ?

Core Java

Ans. String has an argument constructor that take char array as argument and creates a string.

There is no constructor available with String that takes in a character and creates a String. We can use StringBuilder which has a char argument constructor.

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Q1984. Explain Generics in Java ?

Core Java

Ans. Generics are a facility of generic programming that were added to the Java programming language in 2004 within J2SE5.0. They allow "a type or method to operate on objects of various types while providing compile-time type safety.

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Q1985. What is ORM or Object Relationship Mapping ?

Database

Ans. ORM is the mapping technique, which maps object with relational data model. As we know that in java we need objects we can not user data in relational(in table form). So ORM is set of guideline which allows us to map relational data model in object form.

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Q1986. What are the uses of Abstraction ?

Core Java

Ans. Loose Coupling
Facilitates designing complex applications by making them modular.

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Q1987. What are the disadvantages of Bean Auto Wiring in Spring ?

Spring

Ans. It can always be overridden with explicit wiring. Moreover it's confusing if we use both explicit as well as explicit wiring in the project.

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Q1988. How can we track of all objects created in an application ?

Design

Ans. We can store the references in a collection by adding to those objects in the collection. We can create a class "ObjectRegistry" with a collection or multiple collections with a search algorithm to look for the already collected objects.

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Q1989. Why is JVM called Virtual machine ?

Core Java

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Q1990. Lets say we have a set "set1" with objects of Class A, Class has a non static string called element1, Write a code ( using lambda expression ) to see if there is any object in the set with element1 = "Hello".

Core Java

Ans. set1.stream().filter(p->p.element1.equals("Hello")).findAny().isPreent();

or

set1.stream().map(A::getElement1).anyMatch("Hello"::equals)

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Q1991. Which of the OOP's features facilitate dependency injection ?

Design

Ans. Inheritance , Runtime Polymorphism and Composition.

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Q1992. Is Runtime Polymorphism possible without Inheritance ?

Core Java

Ans. Yes, Runtime Polymprohism requires either Class inheritance or Interface implementation.

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Q1993. Is dependency injection possible if we don't have inheritance / Composition ?

Design

Ans. Without composition - No, as it's the core of dependency injection.

With Inheritance - Yes, through interface implementation.

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Q1994. Why is Java such an important Programming language ?

Core Java

Ans. Because of following features

Object Oriented and hence helps build maintainable and easily enhanceable code.
Platform Independence and hence can be executed anywhere
Fast due to JIT compiler

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Q1995. Why Java is considered more purer object oriented language than C++ ?

Core Java

Ans. Because of

lack of use of pointers,
Lack of structural programming and
Lack of Multiple Inheritance

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Q1996. Does Wrapper classes produces immutable objects ?

Core Java

Ans. Yes

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Q1997. Why shouldn't we use string concatenation extensively or in a loop ?

Core Java

Ans. Because String being an immutable object creates a new object upon each concatenation cycle. If there is any such need , we should use String Builder whose objects are mutable.

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Q1998. What do we mean by a Data Type ?

Core Java

Ans. if you have similar type of data or objects or entities, then we can give them a type with unique name. And this name will be our Data type.

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Q1999. As root, if you have to assign the owner for the file and set only read permission for the owner, Write a unix command to do it.

Unix

Ans. chmod 477

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Q2000. In the following code, which text will get printed immediately after Hello

for(int countx=0;countx<10;count++){
System.out.println("World");
for(int countx=0;countx<10;count++){
System.out.println("Friend");
for(int countx=0;countx<10;count++){
System.out.println("Hello");
break;
}
System.out.println("Buddy");
}
}

Core Java

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Q2001. Which of the two - iteration or recursion - is slower ?

Core Java

Ans. Any function call is slower than the code in the same method as Java has to maintain stack of meta and function call information. So recursion is slower.

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Q2002. In case of generic class declared like following , What can T hold

class MyClass<T>{
T element;
}

Core Java

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Q2003. If we have to specify a collection of a particular information like List of addresses, How can we represent that in a JSON ?

JSON

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Q2004. Which type of testing involves use of mocking frameworks ?

Testing

Ans. Unit Testing

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Q2005. Can and Should we mock calls in integration tests ?

Testing

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Q2006. What features would you like to see in Java 10 ?

Core Java

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Q2007. Can we instantiate the object of derived class if parent constructor is private ?

Core Java

Ans. No

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Q2008. How do you design microservices?

Design

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Q2009. Can an enum extend another enum ?

Core Java

Ans. No

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Q2010. Can we have a sub enum within an enum ?

Core Java

Ans. Yes

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