Java fundamentals

Walk through core Java fundamentals, as asked in an entry-level/intern technical screen.

Be ready to discuss

• Language basics: primitives vs. objects, autoboxing, == vs. .equals(), String immutability and the string pool.
• OOP: classes vs. interfaces, inheritance vs. composition, method overloading vs. overriding, access modifiers.
• Collections: ArrayList vs. LinkedList, HashMap internals (hashing, buckets, collisions), HashMap vs. Hashtable vs. ConcurrentHashMap.
• Memory and runtime: stack vs. heap, garbage collection basics, the role of the JVM.
• Exceptions: checked vs. unchecked, try/catch/finally, throw vs. throws.