Competitive coding in Java

From C++ to Java: A Quick-Start Guide

This guide is for competitive programmers who are already comfortable with data structures and algorithms in C++ (or another language) and want to quickly find the Java equivalents.

The goal is not to reteach the concepts, but to map your existing knowledge to Java’s syntax and its powerful standard library.

Core Topics & Equivalents

Here is the breakdown of the topics we will cover. Each section provides the Java alternative to common C++ tools.

1. Fast I/O in Java

   • Replacing cin/cout with BufferedReader and PrintWriter.

2. The Collections Framework: Dynamic Arrays

   • C++ std::vector ↔ Java ArrayList.

3. The Collections Framework: Hash Maps & Sets

   • C++ std::unordered_map ↔ Java HashMap.
   • C++ std::unordered_set ↔ Java HashSet.

4. The Collections Framework: Heaps

   • C++ std::priority_queue ↔ Java PriorityQueue.

5. The Collections Framework: Balanced Trees

   • C++ std::map ↔ Java TreeMap.
   • C++ std::set ↔ Java TreeSet.

6. Stacks, Queues, and Deques

   • C++ std::queue ↔ Java Queue<T> q = new LinkedList<>();
   • C++ std::stack ↔ Java Deque<T> s = new ArrayDeque<>();
   • C++ std::deque ↔ Java Deque<T> d = new ArrayDeque<>();

7. Essential Utilities

   • Custom sorting with Arrays.sort() and Collections.sort().
   • Handling arbitrarily large numbers with BigInteger.