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Q1971. How can we convert char into a String ?

Ans. We can use StringBuilder. StringBuilder accepts char as the argument for it's constructor.

new StringBuilder('').toString();

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Q1972. How can we check if a particular character is upper case in Java ?

Core Java

Ans. 1. We can compare the ascii value of the character. Ascii for Capital case character is from 65 to 90.

2. We can compare to see if lowerCase of the character is not equal to character itself.

For example -

if character is 'a' the following code

new StringBuilder(char).toString().toLowerCase().equals(new StringBuilder(char)

will return true and hence char is lower case

if character is 'A' the following code

new StringBuilder(char).toString().toLowerCase().equals(new StringBuilder(char)

will return false and hence char is upper case

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Q1973. How different is it when final applied to variables and object references ?

Core Java

Ans. final when assigned to object references doesn't make them immutable. It means that the references cannot be de-referenced.

final when applied to variables means that the value cannot be changed.

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Q1974. Why the following code produced this output ?

int x = 5;
int y = x;
y = 10;

System.out.println(x); // prints 5 and not 10

Core Java

Ans. Because when we say y = x, the value of x is copied to another memory location and then y points to that new memory location.

Unlike object references that once assigned point to same object in memory, value is copied in case of variable assignment.

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Q1975. In which memory segment - heap or stack, the following stored by JVM

1. static members
2. objects
3. object references
4. local or method variables

Core Java

Ans. static members are stored in method area of heap

objects are stored on heap

object references are stored on stack

local or method variables are stored on stack

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Q1976. Write a Program to implement stack using LinkedList.

Data Structure

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Q1977. Describe how you could use a single array to implement three stacks

Algorithm

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Q1978. How would you design a stack which, in addition to push and pop, also has a function min which returns the minimum element? Push, pop and min should all operate in O(1) time

Algorithm

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Q1979. 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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Q1980. 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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Q1981. 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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Q1982. 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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Q1983. 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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Q1984. What are the uses of Abstraction ?

Core Java

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

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Q1985. 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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Q1986. 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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Q1987. Why is JVM called Virtual machine ?

Core Java

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Q1988. 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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Q1989. Which of the OOP's features facilitate dependency injection ?

Design

Ans. Inheritance , Runtime Polymorphism and Composition.

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Q1990. Is Runtime Polymorphism possible without Inheritance ?

Core Java

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

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Q1991. 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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Q1992. 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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Q1993. 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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Q1994. Does Wrapper classes produces immutable objects ?

Core Java

Ans. Yes

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Q1995. 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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Q1996. 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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Q1997. 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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Q1998. 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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Q1999. 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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Q2000. In case of generic class declared like following , What can T hold

class MyClass<T>{
T element;
}

Core Java

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