CodeBlanks

Sahay Karo

About this app

CodeBlanks teaches Java by doing, not reading.

Each problem shows you a working solution with key lines blanked out. You pick the right token from a pool and snap it into place — building real code from the inside out, not copy-pasting from a hint.

Stuck? The built-in AI tutor gives Socratic hints at 4 levels:
• Nudge — points you in the right direction
• Hint — explains the concept
• Pseudocode — shows the logic without the syntax
• Guided code — walks you through the solution

87 problems from easy to hard, organised by the Google 30-day interview list: arrays, strings, hash maps, trees, graphs, dynamic programming, and more.

No account needed. No data stored. Just open and practise.

Earn extra AI hints by watching a short rewarded ad.

What’s new

New: Refresh — a swipeable feed of quick Java & Spring Boot concept flashcards, with an AI chat for follow-up questions, search, session length options, and optional daily reminders. Also includes review-priority ordering so concepts you flagged as tricky resurface sooner.