Microservice_Lesson_2: Design Patterns, Creational Design Patterns

 






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Interview questions

Изображение
+1. JVM memory areas. Thread safe memory areas, Garbage collector working principle, Java reference types +2. SOLID +3. Collection API: How does HashMap work under the hood, hash collision, Concurrent HashMap +4. Equals and HashCode contract -5. Thread, Volatile vs Synchronized, atomic variables(CAS-compare and swap). How to prevent deadlock. Deadlock vs livelock. Reentrant lock. +6. Error vs Exception +7. Immutable class(how to make object properties immutable, immutable collections) +8. DB index type(clustered, non clustered, composite) +9. DB normalization and denormalization +10. RDBMS vs non RDBMS +11. ACID vs BASE. Lock mechanism +12. Hash eviction policy(TTL, LRU, FIFO, LFU, MRU, random replacement, ARC). Problem: we have 2GB memory, how to store 15GB data in this cache +13. entity lifecycle +14. dirty check, flush +15. cascade types +16. n+1 problem (entity graph, join fetch) +17. lazy initialization exception 18. idempotency, safe in rest methods +19. IOC, DI, Proxy +20. AOP(c...
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Lesson1: JDK, JVM, JRE

Изображение
1. Compiler - takes the entire programming code written in high language and translates the whole of it into machine code at once. After this process the an executable file will be ready to run. The translation takes some times to be done, but after that execution is so fast. 2. Interpreter - takes each single instructions of the code translates it and then executes it on its own. The translation step is before the program runs is fast, but execution is slow. JDK = JRE + development tools JRE = JVM + library class JDK -> Java Development Kit. A kit which provides the environment to develop and execute (run) Java program. JRE -> Java Runtime Environment. Provides environment to only run. JVM -> Java Virtual Machine f * Compiled: Fortran, C, C++, Pascal, Haskell, Rust, Go * Interpreted: JavaScript, PHP, Python, Ruby Java both compiled and interpreted language. Terminalda : javac Main.java yazdiqda, source fayli(.java) bytecode(.class) faylina cevirir. Terminalda: java Main (bu z...
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MS Lesson26: Threads

Изображение
1. Process - emeliyyat sistemi terefinden ishe salinan, oz ayrica yaddash sahesine malik olan programin icra nusxesidir.  Mes biz kompumuzda muxtelif programlar acanda Paint, Excel ve s. bunlar ferqli proseslerdir.  OS her bir prosese ferqli registerler, stack memory, heap memory assign edir.  Restoran misali: Restoran = process Bina = yaddash (RAM) Ishciler = thread Yeni process ishe salinmish bir programdir. * Her proses oz yaddashinda ishleyir, bashqasina toxuna bilmez. * OS her prosese unikal ID verir. * Yaratmaq / silmek bahalidir. * Biri crash olsa, digerine tesir etmir.  Bir prosesin icinde coxlu thread ola biler. Amma bir thread yalniz bir prosese aid ola biler.  Java kodu bashlayanda JVM ozu de bir nece thread yaradir: * main thread - bizim kodumuz * GC thread - Garbage Collector * Finalizer thread * Signal Dispatcher thread 2. Thread - process icinde ishleyen ayrica ish axinidir. Kodun setir setir icra olundugu yoldur.  Restoran - process Ashpaz 1...
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