Java 8 Interview Questions and Answers

Last update: 11 Mar 2022, 25 Questions

JAVA is an open-source object-oriented programming language that is secure and robust. JAVA is the language that can run on all the platforms which support JAVA without recompilation. More than 3 billion devices run on Java. JAVA is used for developing Mobile applications, Desktop applications, Web servers, and application servers etc.JAVA was developed by James Gosling at Sun Microsystems now ORACLE in the year 1995.

The Java 8 interview questions we are mentioning below will help you to gain enough of the knowledge about Fortran.

Advantages Of Java 8
  • Introduction of Lambda Expression- first step to functional programming
  • New stream API to supports pipeline processing.
  • Optional − Emphasis on handling null values properly.
  • Nashorn Engine- Provides better performance than Rhino javascript engine.
What is JAVA 8? JAVA 8 is one of the versions of JAVA programming which was released on March 18, 2014.
Latest Version Java SE 1317th September 2019
Developed By Sun Microsystems
Designed By James Gosling

Most Frequently Asked Java 8 Interview Questions

Here in this article, we will be listing frequently asked Java 8 Interview Questions and Answers with the belief that they will be helpful for you to gain higher marks. Also, to let you know that this article has been written under the guidance of industry professionals and covered all the current competencies.

1. What is the difference between intermediate and terminal operations?
S.no Intermediate Terminal
1. The intermediate operation produces stream pipelining Terminal operation terminate the pipeline
2. Intermediate operations can be chained multiple times on a stream Terminal operations cannot be chained various times.
3. Intermediate operations cannot be evaluated independently; it needs a terminal operation for evaluation. Terminal Operations can be evaluated independently.
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2. What is the purpose of functional interface in Java 8?

Functional interfaces are those interfaces that have a single functionality.


  • CompareTo--- This interface is only for comparison purposes.
  • Function---this interface accepts only one argument and gives the result.
  • This interface means that an object is tested to be either true or false.
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3. What are the new features in Java 8?
New features introduced in Java 8 are:-
  • Introduction of Lambda Expression- first step to functional programming
  • New stream API to support pipeline processing.
  • Optional − Emphasis on handling null values properly.
  • Nashorn Engine- Provides better performance than Rhino javascript engine.
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4. What is a Java Lambda Expression?

Lamba expression is considered as the most significant feature of Java8. A Lambda expression provides functional programming, and that has simplified the code to a great extent. A lambda expression is fundamentally a function which can be created without belonging to any class.

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5. What is method reference in Java 8?

Method references support in pointing to the methods by their names. A method reference is denoted by using "::" symbol. A method reference is used to indicate the following methods

  • Static methods
  • Instance methods
  • Constructors using new operator (TreeSet::new)

This is a fundamental question in java 8 interview questions.

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6. What do you mean by of String::valueOf expression in Java 8?

The valueOf() method converts data into human-readable form.So String valueOf() will return the string representation of the value. The valueOf() method is a static method.

  • String valueOf(inum)--this syntax will return the string representation of the integer inum.
  • String.valueOf(data, 0, 5)-- This syntax will return the string representation of the character Array 0 to 5
  • String.valueOf(fNum) --this syntax will return the string representation of the float fNum
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7. What is Optional in Java 8?

In java there a NullPointerException which can crash the code. It is complicated to remove the null checks from the code. Java 8 introduced Optional class in java. util package. Use of Optional class results in clean code without null checks. By using the Optional class, the programmer can specify the other value or other code to return. This makes the code more readable.

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8. What is the use of default method in interface?

The default method implementation was introduced by Java 8 so that the old interfaces can use the lambda expression without implementing the methods in the implementation class.




public interface interview {

        default void print() {

System.out.println("Welcome Bestinterviewquestion.com");



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9. What is the syntax and characteristics of a Lambda Expression in JAVA 8?

The syntax for the Lambda expression is:-

parameter -> expression body

Characteristics of the Lambda Expression:-
  • No need to declare the parameter type as the compiler will get the standard by the value of the parameter.
  • For the multiple parameters parenthesis has to be declared, but for the simple parameter, parenthesis need not be declared.
  • If a contains only a single parameter, then there is no need of curly braces.
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10. Define Nashorn in Java8.

Along with Java 8, a new improved engine Nashorn was introduced. Nashorn gives very high performance because it straightaway compiles the program code in the memory and then passes the bytecode to JVM. It uses the invoke dynamics feature of Java 7 to improve the performance.

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11. What is the difference between collection and stream?
S.no Collection API Stream API
1. Collection API is for storing the data in the different kinds of data structures. Stream API is not a data structure; it is used for computation of the data on the big set of objects
2. A finite number of elements can be stored in a data structure An infinite number of features can be stored
3. Consumption of elements is multiple times Consumption of elements is only once.
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12. What is Spliterator in Java 8?

A Spliterator is a type of Java8 Iterator in java. util package that traverses and partitions the elements of a source in Java into another Spliterator. A source can be a collection or an IO channel or a generator function

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13. What do you mean by JJS in Java8?

Java 8 introduced a command tool jjs for the Nashorn to execute the javascript program codes at the console.

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14. What is Stream API in Java8?

The Stream API is used to process a group of objects. A stream is a series of objects which supports different methods that can be pipelined to produce the expected result.

The features of the stream are –
  • A stream takes the input from the Collections, an Arrays or the I/O channels.
  • Streams don’t alter the original data structure; they only give the result according to the pipelined methods.
  • Each intermediate operation is executed in a lazy manner, and as a result, it returns a stream. Hence various intermediate processes can be pipelined. The terminal operations remain at the end of the pipelining process. It replaces the final value, and the pipeline is terminated.
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15. What are the difference between map and flatMap stream operation in Java 8?
S.no Map Flat map
1. For one input value, it gives one output value For one input value,e it produces the arbitrary number
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16. What do you mean by stream pipelining in Java 8?

Stream Pipelining is done by dividing the operations which can happen on the flow into two categories. The first is Intermediate operations and the second is Terminal operations. The common operations return the stream itself so that the result can be pipelined. The terminal operations remain at the end of the pipelining operation. It returns the final value, and the pipeline is terminated.

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17. Write a program to print 15 random numbers using forEach of java 8?

Random random = new Random();

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18. Write a program to print count of empty strings in java 8?

The code to print the count of empty strings in Java 8 is:-

List strings = Arrays.asList("abc", "", "bc", "efg", "abcd","", "jkl");
//get a count of empty string
long count = strings.p
arallelStream().filter(string -> string.isEmpty()).count();

Point to be noted: Go through this Q&A very thoroughly as this is one of the most asked java 8 interview questions.


List<String>strings = Arrays.asList("abc", "", "bc", "efg", "abcd","", "jkl");
int count = strings.stream().filter(string −> string.isEmpty()).count();
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19. What is sequential and parallel stream in Java 8?

Parallel streams divide the provided venture into many and run them in unique threads, making use of a couple of cores of the computer. On the other hand, sequential streams work just like for-loop the use of a single core. The duties supplied to the streams are generally the iterative operations performed on the factors of a series or array or from different dynamic sources. Parallel execution of streams run more than one iterations concurrently in extraordinary accessible cores.

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20. What do you mean by collectors in Java 8?

Collectors perform the reduction operations. It combines the result of the processing ongoing on the elements of the stream like collecting the elements into collections, summarizing the elements according to the different criteria. Collectors return the list or a string. As a result, the readability is increased. Static import used here is static import java.util.stream.Collectors.*;

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21. Explain local datetime API in Java8?

In new data-time API, one of the class is Local Date-Time API where there is no problem of handling of the time-zones. Programmers use this API where time zones are not required. Local Date-Time API is defined in the package java.time

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22. What do you mean by chromounits in java8?

The Chrono unit was added in Java 8 to replace those integer value that was used in old API to represent the month, day, year, etc. unit is defined in the java.time.temporal.ChronoUnit

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23. What is type inference in Java8?

Type inference is a feature of Java that gives the capability to the compiler to seem at each method invocation and corresponding announcement to determine the type of arguments. Java provides multiplied model of type inference in Java eight

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What is JAVA 8?

JAVA 8 is one of the versions of JAVA programming language which was released on March 18, 2014. Java8 provides supports for functional programming, new JavaScript engine Nashorn, new APIs for the date and time manipulation, new streaming API, etc. Now the coding has become simple.

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