salira technology interview question

salira technology ( call based 2016, 2017 batch )

drive date 7 april

No: 43, K.No: 339, 1st Main,1st Cross, Abirudhi Layout T.C. Palya,Krishnarajapuram Hobli, Bangalore Bangalore KA 560016 IN
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for interview question check these links
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1. What is JavaScript?

JavaScript is a client-side as well as server side scripting language that can be inserted into HTML pages and is understood by web browsers. JavaScript is also an Object based Programming language

2. Enumerate the differences between Java and JavaScript?

Java is a complete programming language. In contrast, JavaScript is a coded program that can be introduced to HTML pages. These two languages are not at all inter-dependent and are designed for the different intent. Java is an object – oriented programming (OOPS) or structured programming language like C++ or C whereas JavaScript is a client-side scripting language.

3. What are JavaScript Data Types?

Following are the JavaScript Data types:

Number
String
Boolean
Function
Object
Undefined
4. What is the use of isNaN function?

isNan function returns true if the argument is not a number otherwise it is false.

5. Between JavaScript and an ASP script, which is faster?

JavaScript is faster. JavaScript is a client-side language and thus it does not need the assistance of the web server to execute. On the other hand, ASP is a server-side language and hence is always slower than JavaScript. Javascript now is also a server side language (nodejs).

javascript-code-snippet
Javascript

6. What is negative infinity?

Negative Infinity is a number in JavaScript which can be derived by dividing negative number by zero.

7. Is it possible to break JavaScript Code into several lines?

Breaking within a string statement can be done by the use of a backslash, ‘\’, at the end of the first line

Example:

document.write(“This is \a program”);
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document.write(“This is \a program”);
And if you change to a new line when not within a string statement, then javaScript ignores break in line.

Example:

var x=1, y=2,
z=
x+y;
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var x=1, y=2,

z=

x+y;
The above code is perfectly fine, though not advisable as it hampers debugging.

8. Which company developed JavaScript?

Netscape is the software company who developed JavaScript.

9. What are undeclared and undefined variables?

Undeclared variables are those that do not exist in a program and are not declared. If the program tries to read the value of an undeclared variable, then a runtime error is encountered.

Undefined variables are those that are declared in the program but have not been given any value. If the program tries to read the value of an undefined variable, an undefined value is returned.

10. Write the code for adding new elements dynamically?


t1

firstP



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t1

firstP



11. What are global variables? How are these variable declared and what are the problems associated with using them?

Global variables are those that are available throughout the length of the code, that is, these have no scope. The var keyword is used to declare a local variable or object. If the var keyword is omitted, a global variable is declared.

Example:

// Declare a global globalVariable = “Test”;

The problems that are faced by using global variables are the clash of variable names of local and global scope. Also, it is difficult to debug and test the code that relies on global variables.

12. What is a prompt box?

A prompt box is a box which allows the user to enter input by providing a text box. Label and box will be provided to enter the text or number.

13. What is ‘this’ keyword in JavaScript?

‘This’ keyword refers to the object from where it was called.

14. Explain the working of timers in JavaScript? Also elucidate the drawbacks of using the timer, if any?

Timers are used to execute a piece of code at a set time or also to repeat the code in a given interval of time. This is done by using the functions setTimeout, setInterval and clearInterval.

The setTimeout(function, delay) function is used to start a timer that calls a particular function after the mentioned delay. The setInterval(function, delay) function is used to repeatedly execute the given function in the mentioned delay and only halts when cancelled. The clearInterval(id) function instructs the timer to stop.

Timers are operated within a single thread, and thus events might queue up, waiting to be executed.

15. Which symbol is used for comments in Javascript?

// for Single line comments and

/* Multi

Line

Comment

*/

16. What is the difference between ViewState and SessionState?

‘ViewState’ is specific to a page in a session.

‘SessionState’ is specific to user specific data that can be accessed across all pages in the web application.

17. What is === operator?

=== is called as strict equality operator which returns true when the two operands are having the same value without any type conversion.

18. Explain how can you submit a form using JavaScript?

To submit a form using JavaScript use document.form[0].submit();

document.form[0].submit();

19. Does JavaScript support automatic type conversion?

Yes JavaScript does support automatic type conversion, it is the common way of type conversion used by JavaScript developers

20. How can the style/class of an element be changed?

It can be done in the following way:

document.getElementById(“myText”).style.fontSize = “20?;
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document.getElementById(“myText”).style.fontSize = “20?;
or

document.getElementById(“myText”).className = “anyclass”;
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document.getElementById(“myText”).className = “anyclass”;
21. Explain how to read and write a file using JavaScript?

There are two ways to read and write a file using JavaScript

Using JavaScript extensions
Using a web page and Active X objects
22. What are all the looping structures in JavaScript?

Following are looping structures in Javascript:

For
While
do-while loops
23. What is called Variable typing in Javascript?

Variable typing is used to assign a number to a variable and the same variable can be assigned to a string.

Example

i = 10;
i = “string”;
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i = 10;

i = “string”;
This is called variable typing.

24. How can you convert the string of any base to integer in JavaScript?

The parseInt() function is used to convert numbers between different bases. parseInt() takes the string to be converted as its first parameter, and the second parameter is the base of the given string.

In order to convert 4F (of base 16) to integer, the code used will be –

parseInt (“4F”, 16);
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parseInt (“4F”, 16);
25. Explain the difference between “==” and “===”?

“==” checks only for equality in value whereas “===” is a stricter equality test and returns false if either the value or the type of the two variables are different.

26. What would be the result of 3+2+”7″?

Since 3 and 2 are integers, they will be added numerically. And since 7 is a string, its concatenation will be done. So the result would be 57.

27. Explain how to detect the operating system on the client machine?

In order to detect the operating system on the client machine, the navigator.platform string (property) should be used.

28. What do mean by NULL in Javascript?

The NULL value is used to represent no value or no object. It implies no object or null string, no valid boolean value, no number and no array object.

29. What is the function of delete operator?

The functionality of delete operator is used to delete all variables and objects in a program but it cannot delete variables declared with VAR keyword.

30. What is an undefined value in JavaScript?

Undefined value means the

Variable used in the code doesn’t exist
Variable is not assigned to any value
Property doesn’t exist
31. What are all the types of Pop up boxes available in JavaScript?

Alert
Confirm and
Prompt
32. What is the use of Void(0)?

Void(0) is used to prevent the page from refreshing and parameter “zero” is passed while calling.

Void(0) is used to call another method without refreshing the page.

33. How can a page be forced to load another page in JavaScript?

The following code has to be inserted to achieve the desired effect:


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34. What is the data type of variables of in JavaScript?

All variables in the JavaScript are object data types.
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java interview question
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Q1. Explain JVM, JRE and JDK?
JVM (Java Virtual Machine): It is an abstract machine. It is a specification that provides run-time environment in which java bytecode can be executed. It follows three notations:

Specification: It is a document that describes the implementation of the Java virtual machine. It is provided by Sun and other companies.
Implementation: It is a program that meets the requirements of JVM specification.
Runtime Instance: An instance of JVM is created whenever you write a java command on the command prompt and run the class.
JRE (Java Runtime Environment) : JRE refers to a runtime environment in which java bytecode can be executed. It implements the JVM (Java Virtual Machine) and provides all the class libraries and other support files that JVM uses at runtime. So JRE is a software package that contains what is required to run a Java program. Basically, it’s an implementation of the JVM which physically exists.

JDK(Java Development Kit) : It is the tool necessary to compile, document and package Java programs. The JDK completely includes JRE which contains tools for Java programmers. The Java Development Kit is provided free of charge. Along with JRE, it includes an interpreter/loader, a compiler (javac), an archiver (jar), a documentation generator (javadoc) and other tools needed in Java development. In short, it contains JRE + development tools.

Refer to this below image and understand how exactly these components reside:

Components – Java Interview Questions – Edureka

Q2. Explain public static void main(String args[]).
public : Public is an access modifier, which is used to specify who can access this method. Public means that this Method will be accessible by any Class.
static : It is a keyword in java which identifies it is class based i.e it can be accessed without creating the instance of a Class.

void : It is the return type of the method. Void defines the method which will not return any value.

main: It is the name of the method which is searched by JVM as a starting point for an application with a particular signature only. It is the method where the main execution occurs.

String args[] : It is the parameter passed to the main method.

Q3. Why Java is platform independent?
Platform independent practically means “write once run anywhere”. Java is called so because of its byte codes which can run on any system irrespective of its underlying operating system.

Q4. Why java is not 100% Object-oriented?
Java is not 100% Object-oriented because it makes use of eight primitive datatypes such as boolean, byte, char, int, float, double, long, short which are not objects.

Q5. What are wrapper classes?
Wrapper classes converts the java primitives into the reference types (objects). Every primitive data type has a class dedicated to it. These are known as wrapper classes because they “wrap” the primitive data type into an object of that class. Refer to the below image which displays different primitive type, wrapper class and constructor argument.

WrapperClass – Java Interview Questions – Edureka

Q6. What are constructors in Java?
In Java, constructor refers to a block of code which is used to initialize an object. It must have the same name as that of the class. Also, it has no return type and it is automatically called when an object is created.

There are two types of constructors:

Default constructor
Parameterized constructor
Q7. What is singleton class and how can we make a class singleton?
Singleton class is a class whose only one instance can be created at any given time, in one JVM. A class can be made singleton by making its constructor private.

Q8. What is the difference between Array list and vector?
Array List Vector
Array List is not synchronized. Vector is synchronized.
Array List is fast as it’s non-synchronized. Vector is slow as it is thread safe.
If an element is inserted into the Array List, it increases its Array size by 50%. Vector defaults to doubling size of its array.
Array List does not define the increment size. Vector defines the increment size.
Array List can only use Iterator for traversing an Array List. Except Hashtable, Vector is the only other class which uses both Enumeration and Iterator.
Q9. What is the difference between equals() and == ?
Equals() method is defined in Object class in Java and used for checking equality of two objects defined by business logic.
“==” or equality operator in Java is a binary operator provided by Java programming language and used to compare primitives and objects. public boolean equals(Object o) is the method provided by the Object class. The default implementation uses == operator to compare two objects. For example: method can be overridden like String class. equals() method is used to compare the values of two objects.

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public class Equaltest {
public static void main(String[] args) {
String str1= new String(“ABCD”);
String str2= new String(“ABCD”);
if(Str1 == str2)
{
System.out.println(“String 1 == String 2 is true”);
}
else
{
System.out.println(“String 1 == String 2 is false”);
String Str3 = Str2;
if( Str2 == Str3)
{
System.out.println(“String 2 == String 3 is true”);
}
else
{
System.out.println(“String 2 == String 3 is false”);
}
if(Str1.equals(str2))
{
System.out.println(“String 1 equals string 2 is true”);
}
else
{
System.out.prinltn(“String 1 equals string 2 is false”);
}
}}
Q10. What are the differences between Heap and Stack Memory?
The major difference between Heap and Stack memory are:

Features Stack Heap
Memory Stack memory is used only by one thread of execution. Heap memory is used by all the parts of the application.
Access Stack memory can’t be accessed by other threads. Objects stored in the heap are globally accessible.
Memory Management Follows LIFO manner to free memory. Memory management is based on generation associated to each object.
Lifetime Exists until the end of execution of the thread. Heap memory lives from the start till the end of application execution.
Usage Stack memory only contains local primitive and reference variables to objects in heap space. Whenever an object is created, it’s always stored in the Heap space.

In case you are facing any challenges with these java interview questions, please comment your problems in the section below. Apart from this Java Interview Questions Blog, if you want to get trained from professionals on this technology, you can opt for a structured training from edureka! Click below to know more.

Get Started with Java

OOPS Java Interview Questions:
Q1. What is Polymorphism?

Polymorphism is briefly described as “one interface, many implementations”. Polymorphism is a characteristic of being able to assign a different meaning or usage to something in different contexts – specifically, to allow an entity such as a variable, a function, or an object to have more than one form. There are two types of polymorphism:

Compile time polymorphism
Run time polymorphism

Compile time polymorphism is method overloading whereas Runtime time polymorphism is done using inheritance and interface.

Q2. What is runtime polymorphism or dynamic method dispatch?
In Java, runtime polymorphism or dynamic method dispatch is a process in which a call to an overridden method is resolved at runtime rather than at compile-time. In this process, an overridden method is called through the reference variable of a superclass. Let’s take a look at the example below to understand it better.

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class Car {
void run()
{
System.out.println(“car is running”);
}
}
class Audi extends Car {
void run()
{
System.out.prinltn(“Audi is running safely with 100km”);
}
public static void main(String args[])
{
Car b= new Audi(); //upcasting
b.run();
}
}
Q3. What is the difference between abstract classes and interfaces?
Abstract Class Interfaces
An abstract class can provide complete, default code and/or just the details that have to be overridden. An interface cannot provide any code at all,just the signature.
In case of abstract class, a class may extend only one abstract class. A Class may implement several interfaces.
An abstract class can have non-abstract methods. All methods of an Interface are abstract.
An abstract class can have instance variables. An Interface cannot have instance variables
An abstract class can have any visibility: public, private, protected. An Interface visibility must be public (or) none.
If we add a new method to an abstract class then we have the option of providing default implementation and therefore all the existing code might work properly If we add a new method to an Interface then we have to track down all the implementations of the interface and define implementation for the new method
An abstract class can contain constructors An Interface cannot contain constructors
Abstract classes are fast Interfaces are slow as it requires extra indirection to find corresponding method in the actual class
Q4. What is method overloading and method overriding?
Method Overloading :
In Method Overloading, Methods of the same class shares the same name but each method must have different number of parameters or parameters having different types and order.
Method Overloading is to “add” or “extend” more to method’s behavior.
It is a compile time polymorphism.
The methods must have different signature.
It may or may not need inheritance in Method Overloading.
Let’s take a look at the example below to understand it better.

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class Adder {
Static int add(int a, int b)
{
return a+b;
}
Static double add( double a, double b)
{
return a+b;
}
public static void main(String args[])
{
System.out.println(Adder.add(11,11));
System.out.println(Adder.add(12.3,12.6));
}}
Method Overriding:
In Method Overriding, sub class have the same method with same name and exactly the same number and type of parameters and same return type as a super class.
Method Overriding is to “Change” existing behavior of method.
It is a run time polymorphism.
The methods must have same signature.
It always requires inheritance in Method Overriding.
Let’s take a look at the example below to understand it better.

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class Car {
void run(){
System.out.println(“car is running”);
}
Class Audi extends Car{
void run()
{
System.out.prinltn(“Audi is running safely with 100km”);
}
public static void main( String args[])
{
Car b=new Audi();
b.run();
}
}
Q5. Can you override a private or static method in Java?
You cannot override a private or static method in Java. If you create a similar method with same return type and same method arguments in child class then it will hide the super class method; this is known as method hiding. Similarly, you cannot override a private method in sub class because it’s not accessible there. What you can do is create another private method with the same name in the child class. Let’s take a look at the example below to understand it better.

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class Base {
private static void display() {
System.out.println(“Static or class method from Base”);
}
public void print() {
System.out.println(“Non-static or instance method from Base”);
}
class Derived extends Base {
private static void display() {
System.out.println(“Static or class method from Derived”);
}
public void print() {
System.out.println(“Non-static or instance method from Derived”);
}
public class test {
public static void main(String args[])
{
Base obj= new Derived();
obj1.display();
obj1.print();
}
}
Q6. What is multiple inheritance? Is it supported by Java?
MultipleInheritance – Java Interview Questions – EdurekaIf a child class inherits the property from multiple classes is known as multiple inheritance. Java does not allow to extend multiple classes.

The problem with multiple inheritance is that if multiple parent classes have a same method name, then at runtime it becomes difficult for the compiler to decide which method to execute from the child class.

Therefore, Java doesn’t support multiple inheritance. The problem is commonly referred as Diamond Problem.

Q7. What is association?
Association is a relationship where all object have their own lifecycle and there is no owner. Let’s take an example of Teacher and Student. Multiple students can associate with a single teacher and a single student can associate with multiple teachers but there is no ownership between the objects and both have their own lifecycle. These relationship can be one to one, One to many, many to one and many to many.

Q8. What do you mean by aggregation?
Aggregation is a specialized form of Association where all object have their own lifecycle but there is ownership and child object can not belongs to another parent object. Let’s take an example of Department and teacher. A single teacher can not belongs to multiple departments, but if we delete the department teacher object will not destroy.

Q9. What is composition in Java?
Composition is again specialized form of Aggregation and we can call this as a “death” relationship. It is a strong type of Aggregation. Child object dose not have their lifecycle and if parent object deletes all child object will also be deleted. Let’s take again an example of relationship between House and rooms. House can contain multiple rooms there is no independent life of room and any room can not belongs to two different house if we delete the house room will automatically delete.