Interview Questions
- Object-Oriented Programming (OOP)
- Platform-independent (WORA: Write Once, Run Anywhere)
- Automatic garbage collection
- Multithreading support
- Rich standard library
- JVM (Java Virtual Machine): Executes Java bytecode.
- JRE (Java Runtime Environment): Provides libraries + JVM.
- JDK (Java Development Kit): JRE + Development tools (compiler, debugger).
- Compares memory references.
- .equals() → Compares object values (can be overridden)
- String: Immutable.
- StringBuilder: Mutable, not thread-safe, faster.
- StringBuffer: Mutable, thread-safe, slower.
- Encapsulation → Wrapping data & methods (using classes).
- Inheritance → Reusing properties from another class.
- Polymorphism → One name, multiple forms (method overloading/overriding).
- Abstraction → Hiding details, showing only essentials.
- Abstract Class: Can have abstract + concrete methods, supports inheritance.
- Interface: Only abstract methods (till Java 7), multiple inheritance.
- Overloading: Same method name, different parameters (compile-time).
- Overriding: Child class redefines parent class method (runtime).
- Checked: Must be handled (IOException, SQLException).
- Unchecked: Runtime exceptions (NullPointerException).
- throw: Used to explicitly throw an exception.
- throws: Declares exceptions a method may throw.
- A set of classes & interfaces for storing/manipulating data (List, Set, Map, Queue).
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