Scenario — Let’s say we have two threads. In Thread1, we will increment an integer field “count” by 1. In Thread2, if we see the count is larger than 1, we will print the line “t2 running”. If we loop this run() method 100 times, and each time we are printing…

Before we dive into the question, let’s take a look at some key fields of the class ThreadPoolExecutor class: corePoolSize: the minimum number of workers to keep alive. maximumPoolSize: the capacity of the pool. keepAliveTime: timeout in nanoseconds for idle threads waiting for work. workQueue: the queue used for holding…

There’s one comment I read the other day I found hilarious and so true at the same time: “Developer’s daily job is to write bugs and debug them.” Especially as backend developers, the bugs we encounter are often not as straightforward as frontend developers. We usually need to trace the…

Recently, my project at work almost got delayed because the test coverage rate wasn’t up to the standard. I believe unit test coverage is one of the hard requirements for many developers before we can actually push the code to production. A few days ago, I got to know about…

Imagine we are developing a feature to place an order based on different users: Normal user needs to pay the shipping fee, the shipping fee takes up 10% of the products and there’s no discount provided VIP user also needs to pay a 10% shipping fee but a discount will…

In my job recently, we had to develop a new feature for a website app that requires a user login. After I completed my backend logic and was testing the website with username and password from front end, I encountered some authentication stuff such as Cookie, Session, and Token. I…

Serialization in Java allows us to convert an Object to stream that we can send over the network or save it as file or store in DB for later usage. Especially in the microservices architecture, serialization and deserialization become more critical as we often need to send objects from one…

In some development scenarios, we need to push a business process from one state to another upon some events triggered. In my work, the Spring event-driven structure helped to tackle this situation. Let’s take a look at the example below. In this example, our users will apply for a document. …