Core Java Q&As Archives | Page 4 of 11 | 800+ Java & Big Data Interview Q&As

Blog Archives

« 1 2 3 4 5 6 7 8 … 11 »

05: Q19-Q24 How to create a well designed Java application?

A software application is built by coupling various classes, modules, and components. Without coupling, you can’t build a software system. But, the software applications are always subject to changes and enhancements. So, you need to build your applications such a way that they can not only adapt to growing requirements,...

This content is for 30-Day-Full-Access, 100-Day-Full-Access, 200-Day-Full-Access, and 365-Day-Full-Access members only. Register 80+ Free Java FAQs 80+ Free Big Data FAQs

Already a member? Log in here

06: 10+ Atomicity, Visibility, and Ordering interview Q&A in Java multi-threading

Q1. Why is it important to understand the difference between the “JVM memory model” and the computer “hardware memory model”? A1. 3 reasons why it is important to understand the JVM memory model and computer hardware memory model are: 1) JVM memory model and the physical hardware memory model architectures...

This content is for 30-Day-Full-Access, 100-Day-Full-Access, 200-Day-Full-Access, and 365-Day-Full-Access members only. Register 80+ Free Java FAQs 80+ Free Big Data FAQs

Already a member? Log in here

06: 5 Java FP interview Q&As on category theory & monoids

Q01. What is a category theory from a functional programming language perspective?
A01. The category theory is all about abstracting complexities in computations. OO is good for abstracting over Data, and FP is good for abstracting over behavior.

Composition

“f” and “g”

…

06: HashMap & HashSet and how do they internally work? What is a hashing function?

HashMap & HashSet are not only one of the frequently used data structures, but also one of the popular interview topics. Q1. How does a HashMap store data? A1. As key/value pairs. You can store and retrieve values with the keys. … Read more ›...

This content is for 30-Day-Full-Access, 100-Day-Full-Access, 200-Day-Full-Access, and 365-Day-Full-Access members only. Register 80+ Free Java FAQs 80+ Free Big Data FAQs

Already a member? Log in here

06: Java 8 way of File reading and functionally processing the data

package com.read.file;

import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.stream.Stream;

public class MyFileReader {

    public static void main(String[] args) {
        Path file = Paths.get("C:\\Users\\akumaras\\workspace\\test\\src\\com\\read\\file\\readme.txt");

        try
        {
            //Java 8: Stream class
            Stream<String> lines = Files.lines( file, StandardCharsets.UTF_8 );

            for( String line : (Iterable<String>) lines::iterator )
            {
                System.out.println("read=" + line);
            }

        } catch (Exception e){
            e.printStackTrace();
        }
    }
}

package com.read.file;

import java.nio.charset.StandardCharsets;

import java.nio.file.Files;

import java.nio.file.Path;

import java.nio.file.Paths;

import java.util.stream.Stream;

public class MyFileReader {

public static void main(String[] args) {

Path file = Paths.get("C:\\Users\\akumaras\\workspace\\test\\src\\com\\read\\file\\readme.txt");

try

{

//Java 8: Stream class

Stream<String> lines = Files.lines( file, StandardCharsets.UTF_8 );

for( String line : (Iterable<String>) lines::iterator )

{

System.out.println("read=" + line);

}

} catch (Exception e){

e.printStackTrace();

}

Output:

read=A big brown fox
read=jumped over the fence

1 2	read=A big brown fox read=jumped over the fence

#1 double colon notation ::

The new double colon (::) operator that Java 8 has to convert a normal method into lambda expression. So,

Instead of:

list.forEach(n -> System.out.println(n));

1	list.forEach(n -> System.out.println(n));

You can do:

list.forEach(System.out::println);

1	list.forEach(System.out::println);

#2 Why is stream::iterator used?

…

06: Java 9 to 20 features interview Q&As – NullPointerExceptions & new String methods

Q01: How does Java 14+ improve on ubiquitous NullPointerException?
A01: Prior to Java 14, it is harder to find the root cause of the exception. Often you have to debug with break points to identify which variable is null. The JVM will print out only the method,

…

06: Java FP – handling checked exceptions

FP error handling – checked exceptions The code below breaks the flow of execution as the input “ABC” throws a checked exception – “NumberFormatException”.

package com.fp.eg6;

import java.util.stream.Stream;

public class CheckedExceptionWithFPMain {
    
    public static void main(String[] args) {
    
        Stream.of("1", "ABC", "2")
              .map(Integer::parseInt)
              .forEach(System.out::println); // throws checked exception
                                             // java.lang.NumberFormatException
                                             // For "ABC"
    }

}

package com.fp.eg6;

import java.util.stream.Stream;

public class CheckedExceptionWithFPMain {

public static void main(String[] args) {

Stream.of("1", "ABC", "2")

.map(Integer::parseInt)

.forEach(System.out::println); // throws checked exception

// java.lang.NumberFormatException

// For "ABC"

}

Outputs:

1
Exception in thread "main" java.lang.NumberFormatException: For input string: "ABC"
    at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
    at java.lang.Integer.parseInt(Integer.java:580)
    at java.lang.Integer.parseInt(Integer.java:615)
    at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
    at java.util.Spliterators$ArraySpliterator.forEachRemaining(Spliterators.java:948)
    at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
    at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
    at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151)
    at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174)
    at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
    at java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:418)
    at com.fp.eg6.CheckedExceptionWithFPMain.main(CheckedExceptionWithFPMain.java:11)

Exception in thread "main" java.lang.NumberFormatException: For input string: "ABC"

at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)

at java.lang.Integer.parseInt(Integer.java:580)

at java.lang.Integer.parseInt(Integer.java:615)

at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)

at java.util.Spliterators$ArraySpliterator.forEachRemaining(Spliterators.java:948)

at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)

at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)

at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151)

at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174)

at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)

at java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:418)

at com.fp.eg6.CheckedExceptionWithFPMain.main(CheckedExceptionWithFPMain.java:11)

What if you want to just mark all the inputs that throw a “NumberFormatException” … Read more ›...

This content is for 30-Day-Full-Access, 100-Day-Full-Access, 200-Day-Full-Access, and 365-Day-Full-Access members only. Register 80+ Free Java FAQs 80+ Free Big Data FAQs

Already a member? Log in here

06: Q25 – Q32 SOLID design principles interview questions & answers for Java developers

Design principles interview questions & answers for Java developers so that you can expand your OOP skills to design robust Java apps Q25. What are the SOLID design principles? A25. SOLID is an abbreviation for 5 design principles. SRP (Single Responsibility Principle) If you have a class with calculation logic,...

This content is for 30-Day-Full-Access, 100-Day-Full-Access, 200-Day-Full-Access, and 365-Day-Full-Access members only. Register 80+ Free Java FAQs 80+ Free Big Data FAQs

Already a member? Log in here

06: Understanding TimeZones with Java 8 examples

What is UTC? which stands for Coordinated Universal Time. The diagram below shows the standard time offsets of different countries. Some places observe daylight saving time (DST) during their respective summer periods. For example,

Los Angeles (i.e LA) UTC –

…

07: 4 Java FP Functors Interview Q&As

Q01. What do you understand by the terms functors, monads, and applicatives ? A01. Functors, Monads, and Applicatives are concepts or patterns that abstract complexities in computations, and are NOT interfaces or classes. You can think of them as container type classes like List<T>, Option<T>, … Read more ›...

This content is for 30-Day-Full-Access, 100-Day-Full-Access, 200-Day-Full-Access, and 365-Day-Full-Access members only. Register 80+ Free Java FAQs 80+ Free Big Data FAQs

Already a member? Log in here

07: Java 8 API examples using lambda expressions and functional programming

Java 8 API examples using lambda expressions and functional programming. Example 1: The java.lang.Runnable interface has been made a functional interface.

package com.java8.examples;

public class Example1 {
 
 public static void main(String[] args) {
   System.out.println("main thread: " + Thread.currentThread().getName());
   
   //run method takes no arguments so: () -> (body)
   //closure worker thread1
   Runnable r = () -> (System.out.println("worker thread: " + Thread.currentThread().getName())); 
   new Thread(r).start(); //pass the Runnable closure to Thread constructor
   
   //closure worker thread2
   new Thread( () -> (System.out.println("worker thread: " + Thread.currentThread().getName()))).start(); 
 }
}

package com.java8.examples;

public class Example1 {

public static void main(String[] args) {

System.out.println("main thread: " + Thread.currentThread().getName());

//run method takes no arguments so: () -> (body)

//closure worker thread1

Runnable r = () -> (System.out.println("worker thread: " + Thread.currentThread().getName()));

new Thread(r).start(); //pass the Runnable closure to Thread constructor

//closure worker thread2

new Thread( () -> (System.out.println("worker thread: " + Thread.currentThread().getName()))).start();

}

Output: main thread: main worker thread: Thread-0 worker thread: Thread-1 Example 2: The java.util.function package has a number of functional interfaces. … Read more ›...

This content is for 30-Day-Full-Access, 100-Day-Full-Access, 200-Day-Full-Access, and 365-Day-Full-Access members only. Register 80+ Free Java FAQs 80+ Free Big Data FAQs

Already a member? Log in here

07: Java FP – CompletableFuture monadic chaining with examples – part 1

This extends Future Vs. CompletableFuture interview Q&As with Java 8 functional programming (i.e. FP). Q1. Why was CompletableFuture introduced in Java 8 when you already had the Future interface? A1. The CompletableFuture implements both CompletionStage<T> and Future<T> … Read more ›...

This content is for 30-Day-Full-Access, 100-Day-Full-Access, 200-Day-Full-Access, and 365-Day-Full-Access members only. Register 80+ Free Java FAQs 80+ Free Big Data FAQs

Already a member? Log in here

07: Java Iterable Vs Iterator differences and know how

Q1. What are the differences between Iterator<T> Vs Iterable<T>?
A1. The “Iterable” was introduced to be able to use in the “foreach” loop. A class implementing the Iterable interface can be iterated over. For example,

public interface Collection<E> extends Iterable<E>

1	public interface Collection<E> extends Iterable<E>

Hence,

…

« 1 2 3 4 5 6 7 8 … 11 »

Blog Archives

05: Q19-Q24 How to create a well designed Java application?

06: 10+ Atomicity, Visibility, and Ordering interview Q&A in Java multi-threading

06: 5 Java FP interview Q&As on category theory & monoids

06: HashMap & HashSet and how do they internally work? What is a hashing function?

06: Java 8 way of File reading and functionally processing the data

06: Java 9 to 20 features interview Q&As – NullPointerExceptions & new String methods

06: Java FP – handling checked exceptions

06: Q25 – Q32 SOLID design principles interview questions & answers for Java developers

06: Understanding TimeZones with Java 8 examples

07: 4 Java FP Functors Interview Q&As

07: Java 8 API examples using lambda expressions and functional programming

07: Java FP – CompletableFuture monadic chaining with examples – part 1

07: Java Iterable Vs Iterator differences and know how

300+ Java Interview Questions - FAQs

10+ Companion Techs Interview Q&As

300+ Big Data Interview Questions - FAQs

16+ Java Tech Key Areas Interview Q&As

Your Career Tips to go places

Tutorials on Java & Big Data

300+ Java Interview Questions Answered

Disclaimer