Q1. What is RESTful Web service, and why is it favored over SOAP Web service? A1. REST stands for REpresentational State Transfer (REST), which is a stateless software architecture that reads webpages containing XML, JSON, Plain text, etc. REST is a simpler alternative to Simple Object Access Protocol (SOAP) and...
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02: 9 Java Collection interview Q&As on choosing the right data structure
Choosing the right data structure is vital to get the job done with proper space vs performance trade-offs. Q1. What are the common data structures, and where would you use them? A1. Deterministic Data Structures like Arrays, … Read more ›...
02: HTTP basics on headers, MIME types, & cookies for Java developers
Q1. What happens when you open up a browser and type a URL to request a Web page or RESTFul web service data? A1. HTTP is a stateless protocol on top of TCP (Transmission Control Protocol). 1) When the IP address is obtained, … Read more ›...
02: Java 8 Streams, lambdas, intermediate vs terminal ops, and lazy loading with simple examples
A stream is an infinite sequence of consumable elements (i.e a data structure) for the consumption of an operation or iteration. Any Collection<T> can be exposed as a stream. It looks complex, but once you get it, it is very simple. The operations you perform on a stream can either...
02: JDBC with MySQL, Datasource, and connection pool Tutorial
Step 1: pom.xml file with commons-dbcp2 for the connection pooling and abstraction layer for the datasource.
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<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.mytutorial</groupId> <artifactId>simple-persistence</artifactId> <packaging>jar</packaging> <version>1.0-SNAPSHOT</version> <name>simple-persistence</name> <url>http://maven.apache.org</url> <properties> <maven.compiler.source>1.8</maven.compiler.source> <maven.compiler.target>1.8</maven.compiler.target> <java.version>1.8</java.version> </properties> <dependencies> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.12</version> <scope>test</scope> </dependency> <!-- MySQL Driver --> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>6.0.6</version> </dependency> <!-- Connection Pool --> <dependency> <groupId>org.apache.commons</groupId> <artifactId>commons-dbcp2</artifactId> <version>2.1.1</version> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-shade-plugin</artifactId> <executions> <execution> <phase>package</phase> <goals> <goal>shade</goal> </goals> </execution> </executions> </plugin> </plugins> </build> </project> |
db.properties for connection details
Step 2: Create a new source folder “src/main/resources”.
Step 3: Define the MySQL database “learnjavadb” connection properties in a new file named “db.properties”
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02: jvisualvm to detect memory leak – a quick tutorial style Java demo
This is a companion post to 8 Java Memory Management Interview Q&A demonstrating a memory leak scenario step by step with jvisualvm, which is a free profiling tool that gets shipped with JDK. Step 1: Code that causes memory leak Here is a sample code that causes memory leak. …...
02: OOP vs FP with Java example – Conversion strategy pattern
Java code to convert given input values from KM to Meter, Meter to Centimetres, etc. OOP approach using the strategy design pattern Step 1: Define an interface.
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package com.oop.eg2; public interface Converter<T> { T convert(T input); |
Step 2: Define a generic “MyMetricConverter” that implements the “Converter”.
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package com.oop.eg2; import java.math.BigDecimal; public abstract class MyMetricConverter implements Converter<Double> { @Override public Double convert(Double input) { BigDecimal result = BigDecimal.valueOf(input).multiply(BigDecimal.valueOf(getConversionRate())); return result.doubleValue(); } abstract double getConversionRate(); } |
Step 3: Define different strategy classes that return different conversion rates....
03: 12 Java Generics interview Q&As
Q1 What do you understand by the term type erasure with regards to generics? A1. The term type erasure is used in Java generics. In the interest of backward compatibility, robustness of generics has been sacrificed through type erasure. Type erasure takes place at compile-time. … Read more ›...
03: 21+ Java Servlet interview Q&As
Q1. What is a Servlet? Is a Servlet inherently multi-threaded? A1. A Servlet is a Java class that runs within a web container in an application server, servicing multiple client requests concurrently forwarded through the server and the web container. The web browser establishes a socket connection to the host...
03: 7 Things you must know about Java locks and synchronized key word
7 Things you must know about Java locks and synchronized key word summarizes the key basics. #1. Each Java class and object (i.e. instance of a class) has an intrinsic lock or monitor. Don’t confuse this with explicit lock utility class that were added in Java 1.5, … Read more...
03: 9 Core Java Concepts you can’t afford to not know
Q1. How will you go about explaining the following Java concepts to a beginner who is starting to learn Java? 1. Process Vs Threads 2. Heap versus Stack 3. Local variables versus instance variables 4. How do threads communicate with each other? 5. … Read more ›...
03: Java autoboxing & unboxing benefits & caveats interview Q&As
Q1. What do you understand by the terms “autoboxing” and “autounboxing” in Java? A1. Java automatically converts a primitive type like “int” into corresponding wrapper object class Integer. This is known as the autoboxing. When it converts a wrapper object class Integer back to its primitive type “int”, … Read...
03: Java FP composing functions example – calculate discount
FP – calculate the invoice price Invoice Price = (markedPrice * (100 – discountRate)/100) + deliveryCharge Example
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package com.fp.eg3; import java.util.function.Function; public class DiscountCalcFPMain { public static void main(String[] args) { double markedPrice = 300.00; double discountRate = 10.00 ; //10% double deliveryCharge = 50.00; DiscountCalaculator dc = new DiscountCalaculator(); Function<Double, Double> f = dc.currySecondArg((100 - discountRate)/100); Function<Double, Double> g = x -> x + deliveryCharge; Function<Double, Double> h = f.andThen(g); System.out.println("Invoice Price = " + h.apply(markedPrice)); // 320.00 } } |
“f.andThen(g)” is the composition of functions. This can be described as g(f()) where f() is 270.0 (i.e. 300.00 * (100 – … Read more ›...
In 1999, I pivoted from mechanical engineering to become a self-taught Java expert. Over the past 19+ years, I have built a high-demand contracting career, delivering mission-critical solutions for 13+ top-tier organisations. With a proven track record that has generated over 130+ job offers, I help enterprises solve complex data challenges at scale.
Author of the book "Java/J2EE job interview companion", which sold 35,000+ copies on amazon.com & superseded by this site with 2000+ registered users.
Amazon.com profile | LinkedIn | LinkedIn Group | YouTube
Email: java-interview@hotmail.com
Author of the book "Java/J2EE job interview companion", which sold 35,000+ copies on amazon.com & superseded by this site with 2000+ registered users.
Amazon.com profile | LinkedIn | LinkedIn Group | YouTube
Email: java-interview@hotmail.com
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