Interview Questions and Answers for 'L' | Search Interview Question

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Q1921. Name few Threads related classes and interfaces ?

Ans. http://www.buggybread.com/2015/01/java-threads-classes-and-interfaces.html

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Q1922. Name few Boolean classes and interfaces ?

Ans. http://www.buggybread.com/2015/01/java-data-types-double-classes-and_31.html

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Q1923. Name few Double data types related classes and interfaces ?

Ans. http://www.buggybread.com/2015/01/java-data-types-double-classes-and.html

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Q1924. Name few float data type related classes and interfaces ?

Ans. http://www.buggybread.com/2015/01/java-data-types-float-classes-and.html

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Q1925. Name few long data type related classes and interfaces ?

Ans. http://www.buggybread.com/2015/01/java-data-types-long-classes-and.html

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Q1926. Name few Queue classes and interfaces ?

Ans. http://www.buggybread.com/2015/01/java-collections-queue-classes-and.html

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Q1927. What are few iterator classes provided by Java ?

Ans. http://www.buggybread.com/2015/01/java-iterator-classes-and-interfaces.html

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Q1928. Name few File IO related classes and interfaces ?

Core Java

Ans. http://www.buggybread.com/2015/01/java-file-io-classes-and-interfaces.html

Sample Code for File

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Q1929. Name few classes that are part of java.lang package ?

Ans. http://www.buggybread.com/2015/01/java-javalang-classes-and-interfaces.html

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Q1930. Name few classes that are part of java.util package ?

Ans. http://www.buggybread.com/2015/01/java-javautil-classes-and-interfaces.html

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Q1931. Name few Java util classes that were introduced with Java 7 ?

Ans. http://www.buggybread.com/2015/01/migrating-to-java-7-new-classes_25.html

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Q1932. Name few Java Util classes introduced with Java 8 ?

Core Java

Ans. http://www.buggybread.com/2015/01/migrating-to-java-8-new-classes_25.html

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Rarely asked as it was introduced with Java 8.

Q1933. Name few java.lang classes introduced with Java 8 ?

Core Java

Ans. http://www.buggybread.com/2015/01/migrating-to-java-8-new-classes.html

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Q1934. How to make sure that a string contains only Numerals ?

Core Java

Ans. We can use NumberUtils.isNumber which is a part of apache commons package.

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Q1935. What is Jenkins ?

Jenkins

Ans. It is a continuous integration tool written in Java.

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Q1936. What are the various ways in which build can be scheduled in Jenkins ?

Jenkins

Ans. Builds can be triggered by source code management commits.
Can be triggered after completion of other builds.
Can be scheduled to run at specified time ( crons )
Manual Build Requests

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Q1937. Do you know the way to remove unused imports automatically in eclipse ?

Eclipse

Ans. Select the package -> Right Click -> Source -> Organize Imports.

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Q1938. What is Nagios ?

Ans. Nagios is open source system , network and infrastructure monitoring software application. It alerts the user if anything goes wrong. Nagios is widely used as monitoring tool for enterprise applications.

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Q1939. Should we have instance variables in the Spring Bean which has been scoped as Singleton ?

Spring

Ans. No, if required we should only have final variables.Bean scoped singleton means that only one instance of the bean will be created and will be shared among different requests and hence instance variables will get shared too.

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Q1940. What is the difference between Fisheye and Crucible ?

Ans. FishEye is used to extract information from source code repository whereas Crucible is used to request, perform and manage code reviews.

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Q1941. Can we use Fisheye and Crucible independently ?

Ans. Yes

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Q1942. What does the red and green line backgrounds denotes in the crucible code Review ?

Ans. Red Background for a line denotes the lines that have been deleted with the change set and Green background denotes the addition.

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Frequently asked in Tata Consultancy (TCS) interview ( Based on 2 Feedback )

Q1943. What are the technologies used in Jira ?

Tools

Ans. JIRA is written in Java and uses the Pico IOC container,Apache OFBiz entity engine, and WebWork technology stack. For remote procedure calls (RPC), JIRA supports REST, SOAP, and XML RPC.

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Q1944. What are stateless objects ? How are they different from immutable objects ? Which of these two is thread safe ?

Object Oriented Programming

Ans. Stateless objects are the objects without instance fields (instance variables). The class may have compile time constants i.e static final fields.Immutable objects are the objects which have state but the state cannot be changed after initialization. Both are Thread safe.

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Q1945. What are advantages of stateless and / or immutable objects ?

Object Oriented Programming

Ans. They can be shared across multiple threads as they are thread safe.

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Q1946. What are the advantages and disadvantages of static variables and static methods ?

Core Java

Ans. Advantages

Can do meta object operations ( like validating something before creating objects , keep count of number of objects )

Can do operations which have nothing to do with objects but still you want them to be tied to Class.

Disadvantages

Commonly used to static variables sometime leads to problems due to access by different objects.

Are not tied to objects so doesn't reflect pure Object Oriented approach.

Needs to be synchronized so as to avoid update conflicts by mutiple objects and threads.

Some limitation in testing as not all frameworks have facility to mock them. Powermock has but Mockito doesnt

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Q1947. Write code explaining use of Scanner class ?

Ans. Scanner sc = new Scanner(System.in);
int i = sc.nextInt();

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Very Frequently asked. Have been asked in HCL Technologies very frequently ( based on 3 feedback ). Among first few questions in many interviews.

Q1948. Differences between abstract class and interface ?

Core Java

Ans. Abstract classes can have both abstract methods ( method declarations ) as well as concrete methods ( inherited to the derived classes ) whereas Interfaces can only have abstract methods ( method declarations ).

A class can extend single abstract class whereas it can implement multiple interfaces.

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Q1949. In which cases isn't instanceof operator a bad practice?

Core Java

Ans. To avoid ClassCastException.

Though the following code will compile fine but will result in ClassCastException during runtime.

Fruit fruit = new Apple();
Banana banana = Banana(fruit); // ClassCastException

This code will not give compile time error as Banana and Fruit are related as Banana either extends or implement Fruit, So downcasting is acceptable. With this code we assume that the Fruit handler will have the Apple object at that point, violating which the code will throw the exception.

This exception can be avoided by following code.

Fruit fruit = new Apple();
if(fruit instanceOf Banana){
Banana banana = Banana(fruit); // ClassCastException
}

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Try 2 Question(s) Test

Q1950. Difference between Scanner and BufferedReader ? Which one is faster and Why ?

Core Java

Ans. Scanner is used for parsing tokens from the contents of the stream while BufferedReader just reads the stream.

BufferedReader read files efficiently by using a buffer to avoid physical disk operations.

Buffer size of Scanner is usually smaller than the Buffered Writer.

BufferedReader is faster that Scanner as it just reads the Stream and doesn't Parse the tokens to read the stream into primitive data types.

Sample Code for Scanner

Sample Code for BufferedReader

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