CORE JAVA – CONCEPT WISE QUESTIONS

🔹 1️⃣ OOPS (Object Oriented Programming)

Concepts Covered: Class, Object, Inheritance, Polymorphism, Abstraction, Encapsulation

Important Questions:

• What is OOP?
• Difference between class and object?
• Explain encapsulation with example.
• What is inheritance? Types in Java?
• What is polymorphism? (Compile-time vs Run-time)
• What is abstraction?
• Abstract class vs Interface?
• Method overloading vs overriding?
• What is constructor?

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🔹 2️⃣ JVM Architecture

Concepts Covered: JVM, JRE, JDK, Memory Areas

Important Questions:

• What is JVM?
• JDK vs JRE vs JVM?
• Explain JVM memory structure.
• Stack vs Heap memory?
• What is Garbage Collection?

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🔹 3️⃣ Data Types & Variables

Concepts Covered: Primitive, Non-primitive, Wrapper Classes

Important Questions:

• What are primitive data types?
• int vs Integer?
• What is type casting?
• What is auto-boxing & unboxing?

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🔹 4️⃣ Control Statements

Concepts Covered: if, switch, loops

Important Questions:

• while vs do-while?
• break vs continue?
• Can we use String in switch?

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🔹 5️⃣ Strings

Concepts Covered: String, StringBuilder, StringBuffer

Important Questions:

• Why is String immutable?
• String vs StringBuilder vs StringBuffer?
• What is String pool?
• == vs equals()?

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🔹 6️⃣ Exception Handling

Concepts Covered: try, catch, finally, throw, throws

Important Questions:

• What is exception?
• Checked vs Unchecked exceptions?
• What is finally block?
• What is custom exception?

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🔹 7️⃣ Multithreading

Concepts Covered: Thread, Runnable, Synchronization

Important Questions:

• What is thread?
• Process vs Thread?
• How to create thread in Java?
• What is synchronization?
• What is deadlock?

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🔹 8️⃣ Collections Framework

Concepts Covered: List, Set, Map

Important Questions:

• ArrayList vs LinkedList?
• HashMap vs Hashtable?
• What is Iterator?
• Comparable vs Comparator?
• Fail-fast vs Fail-safe?

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🔹 9️⃣ Java 8 Features

Concepts Covered: Lambda, Stream API, Functional Interface

Important Questions:

• What is lambda expression?
• What is functional interface?
• What is Stream API?
• What is default method?

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🔹 🔟 File Handling & IO

Concepts Covered: File, Streams

Important Questions:

• FileInputStream vs FileReader?
• What is serialization?
• What is transient keyword?

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