💻 Sitemap - Java
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What is a variable • Variable Declaration Syntax • Variable Naming Rules • Examples of Valid Names • Basic Data Types (Briefly) • Code — Examples of Types • Declaration vs Initialization • Dynamic Initialization • Scope and Lifetime • Example: Nested Scopes • Initialization Inside a Block • Restriction: you cannot declare the same names in nested scopes • Constants • Recommendations • Homework • Test — How well did you understand the lesson?
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1. Basic truth: Stream vs For — this is not an equal battle • 2. Why for is faster • 3. Why Stream is Slower • 4. Boxing — the main killer of performance • 5. When Stream is NOT worse • 6. When Stream is severely losing • 7. JIT and why the results "float" • 8. CPU cache and call order • 9. Practical Rule for Selection • Use for if: • Use Stream if: • 10. Final Conclusion • ⚔️ Stream vs For in Java — maximum detailed comparative table • ⚡ Stream vs Loop - Code Example with Comments
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1️⃣ HashMap / TreeMap / TreeSet (not thread-safe) • 2️⃣ SynchronizedMap / SynchronizedSortedMap / SynchronizedSortedSet • 3️⃣ ConcurrentHashMap • 4️⃣ ConcurrentSkipListMap / ConcurrentSkipListSet • 5️⃣ AtomicInteger / AtomicReference / AtomicLong • Tables for Comparison: One Element, Two Threads • Table: one element is edited by two threads + new key is added • Comparison of Thread-Safe Sorted Collections • 🔹 Conclusions • 🔹 Practical Rule
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Preface • Comparison of Approaches to Parallelism in Java • 1️⃣ Fork/Join Framework • Key elements: • Example: • 2️⃣ CompletableFuture — asynchronous programming with functional style • Main features: • Example of a CompletableFuture chain: • 3️⃣ Virtual Threads (Project Loom) • Advantages: • Example of Virtual Threads: • 4️⃣ How to Choose the Right Tool • Transition from Threads to Modern Tools • On what basis CompletableFuture makes decisions • Virtual Threads (Project Loom) — The Future of Multithreading in Java • In Brief • Example: Regular Threads vs Virtual Threads • Key Advantages • When to Use • Limitations and Pitfalls • Practical Migration • Summary • Virtual Streams Loom as a Metaverse • Comparison of Approaches to Parallelism in Java and Prerequisites for Choosing • Conclusion
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What the loop consists of • Loop for • Decrementing the counter • Step of changing the counter • Loop while • Loop do...while • Operators break and continue • break — interrupting the loop • continue — jump to the next iteration • Summarizing • Homework • Test — How well did you understand the lesson?
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1) Simple if / else • 2) else if — chain of checks • 3) Comparison Operators and Negation • 4) Logical operators: && (AND) and || (OR) • 5) Ternary Operator — Compact, but Cautious • 6) switch — when there are many discrete options • 7) A small cheat sheet for debugging • Test — How well did you understand the lesson?
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Diagram - Java Memory Model - Heap / Non-Heap / Stack • Java Memory Deep Dive: how objects, primitives and methods live in memory • Java Memory Example: Explanation • Java Caching and GC: how SoftReference affects the life of objects in memory • Java SoftReference Cache Example: Explanation • JIT Compiler with JVM, JIT and Code Cache
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2. Virtual Threads — millions of lightweight threads • ✅ Advantages of Virtual Threads • ❌ Disadvantages of Virtual Threads • 3. GraalVM — universal accelerator • ✅ Advantages of GraalVM • ❌ Disadvantages of GraalVM • 4. Quarkus — Java for Clouds and AI • ✅ Advantages of Quarkus • ❌ Disadvantages of Quarkus • 5. Why this is not a replacement, but maturity • 6. General Direction
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⚡ 1. Simple explanation • 🔥 2. Example: allocations • 3. Where hidden allocations appear • 1. Collections • 2. Streams • 3. String operations • 4. Exceptions • ⚙️ 4. Where Zero Allocation is Really Important • 🚀 5. How Zero Allocation is Achieved • 🧠 6. Important point about JVM • 💣 7. Where Zero Allocation Breaks • 📊 8. Comparison of Approaches • 🏁 Result
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