Java

Java rewards understanding the machinery: what a collection costs, how the JVM turns your source into something that runs, why exceptions are checked. These articles cover the parts that show up in both real code and interview rooms.

17 articles · Free Java course

Collections

Java Streams: Where They Win and Where They Hurt A stream pipeline runs nothing until you ask it for a value, and it will refuse to run twice. Both facts explain most of the confusing bugs beginners hit. Tutorial · 11 min read · August 6, 2026
Java Collections: Pick by Access Pattern, Not Habit LinkedList's famous O(1) insert only applies if you are already holding the node. That one detail explains why the textbook answer loses to ArrayList in real code. Comparison · 12 min read · August 6, 2026
JavaScript sort(): Why [10, 9, 1] Becomes [1, 10, 9] Sorting numbers with plain .sort() gives you an order that looks random until you realise every element was converted to a string first. And the array you sorted was modified, which is its own bug. Tutorial · 11 min read · August 6, 2026
Fixing ArrayIndexOutOfBoundsException in Java Index 5 out of bounds for length 5 is not a mysterious message. It is Java telling you the exact number it received and the exact number it allowed, which is almost the whole fix. Tutorial · 11 min read · August 6, 2026
Java ArrayList Tutorial: Add, Remove, and Iterate A beginner-friendly guide to the Java ArrayList: creating one with generics, the core methods, safe iteration, and how it compares to plain arrays. Tutorial · 9 min read · July 22, 2026
Java HashMap Tutorial: Key-Value Storage Made Easy A beginner-friendly Java HashMap guide: creating maps, storing key-value pairs, handling missing keys, looping, and a word-frequency counter example. Tutorial · 9 min read · July 22, 2026

Java

Collections

Language and OOP

Under the hood

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