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

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Q1801. What will happen if there is a default method conflict as mentioned above and we have specified the same signature method in the base class instead of overriding in the existing class ?

Ans. There won't be any problem as the Base class method will have precedence over the Interface Default methods.

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Q1802. If a method definition has been specified in Class , its Base Class , and the interface which the class is implementing, Which definition will be picked if we try to access it using Interface Reference and Class object ?

Ans. Class method definition is overriding both the definitions and hence will be picked.

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Q1803. If a method definition has been specified in the Base Class and the interface which the class is implementing, Which definition will be picked if we try to access it using Interface Reference and Class object ?

Ans. Base Class Definition will have precedence over the Interface Default method definition.

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Q1804. Can we use static method definitions in Interfaces ?

Core Java

Ans. Yes, Effective Java 8.

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Q1805. Can we have default method with same name and signature in the derived Interface as the static method in base Interface and vice versa ?

Ans. Yes , we can do that as static methods are not accessible using references and hence cannot lead to conflict. We cannot do inverse as Default methods cannot be overridden with the static methods in derived interface.

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Frequently asked at Manhattan Associates ( Based on 2 feedback )

Q1806. What is a Lambda Expression ? What's its use ?

Core Java

Ans. Its an anonymous method without any declaration.

Lambda Expression are useful to write shorthand Code and hence saves the effort of writing lengthy Code.

It promotes Developer productivity, Better Readable and Reliable code.

Sample Code for lambda

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Q1807. Difference between Predicate, Supplier and Consumer ?

Core Java

Ans. Predicate represents an anonymous function that accepts one argument and produces a result.

Supplier represents an anonymous function that accepts no argument and produces a result.

Consumer represents an anonymous function that accepts an argument and produces no result.

Sample Code for Predicate

Sample Code for Supplier

Sample Code for Consumer

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Q1808. What does the following lambda expression means ?

helloJava8 ( x-> x%2 )

Ans. helloJava8 receives an Integer as argument and then returns the modulus of that Integer.

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Q1809. What is the difference between namenode and datanode in Hadoop?

BigData

Ans. NameNode stores MetaData (No of Blocks, On Which Rack which DataNode is stored etc) whereas the DataNode stores the actual Data.

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Q1810. Difference between TCP and UDP ?

Networking

Ans. http://www.cyberciti.biz/faq/key-differences-between-tcp-and-udp-protocols/

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Q1811. What things you would care about to improve the performance of Application if its identified that its DB communication that needs to be improved ?

Solution

Ans. 1. Query Optimization ( Query Rewriting , Prepared Statements )

2. Restructuring Indexes.

3. DB Caching Tuning ( if using ORM )

4. Identifying the problems ( if any ) with the ORM Strategy ( If using ORM )

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Very frequently asked. Usually followed by questions related to private constructor and synchronized access. Frequently asked in JPMorgan and TCS (Based on 2 feedback)

Q1812. Explain Singleton Design Pattern ?

Design

Ans. http://www.buggybread.com/2014/03/java-design-pattern-singleton-interview.html

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Q1813. If I try to add Enum constants to a TreeSet, What sorting order will it use ?

Ans. Tree Set will sort the Values in the order in which Enum constants are declared.

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Q1814. Can we override compareTo method for Enumerations ?

Core Java

Ans. No. compareTo method is declared final for the Enumerations and hence cannot be overriden. This has been intentionally done so that one cannot temper with the sorting order on the Enumeration which is the order in which Enum constants are declared.

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Q1815. How can we test methods individually which are not visible or declared private ?

Ans. We can either increase their visibility and mark them with annotation @VisibleForTesting or can use reflection to individually test those methods.

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Q1816. Write an SQL to find all records having all upper case alphanumeric characters in a field ?

Ans. Select * from Table where field = upper(field)

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Q1817. Write an SQL to find all records having all numeric characters in a field ?

Ans. Select * from Table where isnumeric(field) = 1;

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Q1818. When does an application throw NullPointerException ?

Core Java

Ans. When it tries to access an object element or method using reference which is actually null.

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Q1819. How can we protect an application from throwing a NullPointerException ?

Ans. By having Null Checks.

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Q1820. What are the conventions regarding constant variables or static final variables ?

Core Java

Ans. They should be named all in upper case with underscore separating words.

Moreover the name should be such that it identifies the value. For example, if we are using constant for employee Id 123, it should be named something like EMPLOYEE_ID_123 and not EMPLOYEE_ID

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Q1821. How do you define a class of constants in Java?

Ans. Make the class as final.
Disable the object construction by making constructor private.
Keep only Static Final Variables declared and Defined at the same time.

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Q1822. If you are given a choice to implement the code to either Insert a Record or Update if already exist, Which approach will you follow ?

1. Insert into the DB Table. If exception occurs, update the existing record.
2. Check if the record exists and update it if it exists, If not insert a new record.

Solution

Ans. In first case, there would be 2 DB calls in worst case and 1 in best case. In 2nd approach there will be always 2 DB calls.

Decision on the approach should depend on the following considerations -

1. How costly is the call to DB ? Are we using indices , hibernate etc

If calls to DB are costly , 1st approach should be the choice.

2. Exception Book keeping load upon exception.

The benefit of saving 1st call in approach 1 should be bigger than the Book keeping for the exception.

3. Probability of the exception in first apparoach.

If the DB Table is almost empty, it makes sense to follow Approach 1 as majority of the 1st calls will pass through without exception.

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Q1823. What will the following code do ?

String dateStr = "2011 11 19";
DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
Date date = dateFormat.parse(dateStr);
System.out.println(date);

Ans. It will throw the ParseException as the date format doesn't abide with the format of the specified date.

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Q1824. What will be the output of this code ?

Set mySet = new HashSet();
mySet.add("4567");
mySet.add("5678");
mySet.add("6789");
for(String s: mySet){
System.out.println(s);
}

Ans. It will print 4567,5678 and 6789 but Order cannot be predicted.

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Q1825. What will be the output of this code ?

Set mySet = new TreeSet();
mySet.add("4567");
mySet.add("5678");
mySet.add("6789");
for(String s: mySet){
System.out.println(s);
}

Ans. 4567
5678
6789

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Q1826. What will be the output of this code ?

Set mySet = new HashSet();
mySet.add("4567");
mySet.add("5678");
mySet.add("6789");
System.out.println(s.get(0));

Ans. This will give compile time error as we cannot retrieve the element from a specified index using Set. Set doesn't maintain elements in any order.

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Q1827. public enum Day {
SUNDAY, MONDAY, TUESDAY, WEDNESDAY,
THURSDAY, FRIDAY, SATURDAY
}

public class Test {
Set mySet = new HashSet();
mySet.add(Day.MONDAY);
mySet.add(Day.SUNDAY);
mySet.add(Day.SATURDAY);

for(Day d: mySet){
System.out.println(d);
}
}

Ans. SUNDAY
MONDAY
SATURDAY

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Q1828. Have you ever had problem getting your projects in eclipse refreshed after you made changes in the Pom files ?

Maven

Ans. Yes, It happens many times but I would usually perform mvn eclipse:eclipse and this would resolve the project refresh problems.

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Q1829. What is the difference between compile and install ?

Maven

Ans. Compile compiles the source code of the project

whereas

Install installs the package into the local repository, for use as a dependency in other projects locally

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Q1830. How can we change the JDK compliance level ?

Eclipse

Ans. Windows -> Preferences -> Java - Compiler -> Java Compliance Level

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