- Lambda Expression
A lambda is a function you can pass to a method as if it were a value. That is the whole idea, and it works because of one rule: a lambda is shorthand for implementing an interface that has exactly one abstract method. Understand that rule and lambdas stop looking like magic. Where they came from…
- Memory — Why Structures Have Different Speeds
The stack, the heap, and why an array of a million ints can be faster to scan than a linked list of a million ints even though both are O(n). Contiguous memory, cache lines, pointer chasing, and what a Java object reference really costs.
- Spring Boot – File Upload
Accepting a MultipartFile, the size limits you have to raise in two different places, and validating what was actually uploaded rather than trusting the filename or the content type the browser claimed. Ends with streaming a file back out again.
- Python – Data Types
The types you will use every day — int, float, str, bool, None — plus what a variable really is in Python, why `is` and `==` are not the same question, and the integer division and float rounding traps that bite everyone once.
- Exception Handling
An exception is Java's way of saying "I cannot continue, and here is exactly why". Handling them well is mostly about restraint: catching only what you can actually do something about, and never hiding what you cannot. try , catch , finally The try block holds code that might fail. The catch runs…