A Spring Boot 4.1 tutorial for beginners: set up, run your first app, understand controllers, services and repositories, configuration and validation, then follow a map of 80+ deeper guides.
Spring Framework, Spring MVC and Spring Boot explained by building the same endpoint twice: plain Spring MVC with manual Tomcat vs Spring Boot, with startup time, beans and jar size measured.
A grouped list of the Spring Boot annotations you will actually use, plus the pairs people confuse (@Component vs @Bean, @Controller vs @RestController, @Primary vs @Qualifier) with real output.
Every Spring Boot version from 2.0 to 4.1 with real release dates, free and commercial support end dates, Java baselines, the upgrade path from 2.7 and 3.5, and how to check your version.
30 pattern programs in Java with real output, the row/column logic table and the code for each: pyramids, diamonds, Floyd's and Pascal's triangle, hollow shapes and a method for any pattern.
25 array problems for Java interviews with brute-force and optimal solutions, complexity for each and real output: second largest, rotation, duplicates, missing number, two sum, Kadane and more.
Bubble, selection and insertion sort in Java with pass-by-pass traces, early-exit bubble sort, measured comparison and swap counts, stability and a comparison table.
Factorial in Java with a loop, recursion, streams and BigInteger, showing exactly where int (13!) and long (21!) overflow and computing 100! with BigInteger.
Five Fibonacci implementations in Java with measured call counts, a recursion-tree diagram showing why naive recursion is exponential, memoization, the long overflow at fib(93) and BigInteger.
Reverse a number, palindrome, Armstrong, perfect and strong numbers in Java, each with a dry-run table, real output and the int-overflow trap in reversing.