Java - Wy Lee

Wy Lee

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Java

This tag is about the techniques learned in the field of Java.

Java : Notes on Runtime Exceptions

This article is to recap some common runtime exceptions in Java. It is an important habit to consider exceptions before writing and then deal with them to avoid unintended exceptions during program execution. UnsupportedOperationException Happens when an operation is not supported, often because the implementation does not provide support for

Java : Difference of Arrays.asList() & List.of()

I just want to record the difference between Arrays.asList() and List.of(), as they are used in one of my technical interviews. The purpose is simple : creating a List and manipulating it with stream (nowadays it's much faster to write a collection with stream), and these two

A quick review of interviews

It has been a while since my last post, and I think it is worth taking note of some of my interviews in my journey to landing a job, which I am still working on. During the interviews, I learned a lot, especially from speaking with interviewers who have more

Java : Diving Deeper into Streams

Just delve deeper into Java Streams because I find them very convenient to use. What is Stream API? Stream API is an operation executed on collection, so when we read the code, we can comprehend the code very quickly. It is also called pipelined operation. .filter() .skip() .limit() .distinct() .sorted(

Java : Some notes on Spring Boot

Srping Boot is a solution to * minimize manual config process * provide auto-config based on props files and JAR classpath * resolve dependency conflicts (Maven and Gradle) * provide embeded HTTP server, no need to install tomcat separately Spring Boot contains a complete set of Spring implementations such as MVC / REST / AOP / Core,

Java : IoC / DI / AOP

A recap of the concepts in Java: IoC, DI, and AOP. IoC (Inversion of Control) * Spring has control and does not need to create new instances in the class itself. * To achieve the purpose of decoupling, rely on abstractions rather than instances -Use some Annotation to achieve DI (Dependency Injection)

Java : Polymorphism, Inheritance, and Encapsulation

To record a bit of my rough understanding of polymorphism, inheritance, and encapsulation in Java. Polymorphism * Operate different object / instances under the same interface * Implementation examples * abstract class * Contains at least one abstract method * Leave implementation to inherited classe(s) * No multiple inheritance * Cannot have final declaration * Cannot be instantiated

Java : Wrapper Class

The purpose of using Wrapper class instead of primitive types are * Primitive types do not use new an object to create variables and have their own values. * Because some Java APIs can only use objects (for example, Collection), not primitive types (ie, int, long, char, boolean, etc.) to handle the

Java : Streams and Lambda

The purpose of streams and lambda is to Tell the computer "what to do" instead of "how to do". Below is the example of looping over the colors traditionally. List<String> allColors = List.of("Red", "Blue", "Yellow"); for

Intro of JPA, Hibernate, and ORM

I am writing this article to recap my learning on JPA and Hibernate,as recently I am building my project with this framework. And Hibernate, also a framework to speed up and simplify the process of database connection, is a solution to ORM. Traditionally we use JDBC to implement SQL

Short Circuit: &&, || operator

Short Circuit has two operators, && and II, this article is to introduce its difference between the single operator. boolean result = (false && true); // Because the first result is false, right side will not be evaluated. boolean result = (true || false); // result is true // Same as the or operator.

Data Structure: Overview of List, Set and Map Interface

This post is to record my learning on Data structures in Java. I still remember when I first learned this concept, I felt there were so many things to memorize, so I tried to learn it through understanding. Here is a summary of what I learned about the List, Set,

Switch statement and its use scenario

To review some of the features of switch statement in Java, which is part of the Java foundamental concept, I am writing this article. Also I will introduce it's enhanced statement after Java12. The basics of a switch statement consist of the following: * switch: the statement. * case: how

Java Jmeter test

Over the weekend, I learned about the load testing using JMeter to assess whether our API calls could withstand heavy usage. Steps of Implementation Download 1. Download Jmeter, select any file in Binaries 2. Unzip the entire folder to the desired path Configuration 3. Execute bin/jmeter.bat file 4.