Java

Used during serialization. Fields marked transient are not serialized; after deserialization they take their initial values such as null or 0.

Usage of final on classes, methods, and variables.

1. What the Cloneable interface is. 2. What object cloning is. 3. How to implement object cloning: shallow cloning and deep cloning. 4. References.

Usage and implementation analysis of Integer, including immutability, valueOf, IntegerCache, and autoboxing behavior.

What ArrayList is, how to use it, and source analysis of construction, add, remove, resizing, and fail-fast behavior.

What Hashtable is, how to use it, and source analysis of construction, synchronized put/get/remove/containsKey, hashing, chaining, and rehashing.

Methods on Object, the equals/hashCode contract, and the difference between wait and sleep.

1. What PriorityQueue is. 2. Usage. 3. Source analysis: fields, constructors, heapify, insertion, deletion, sift-up, and sift-down. 4. Reference.

Serialization and deserialization in Java, custom readObject/writeObject hooks, implementation flow, serialVersionUID, and serialization algorithm.

What HashSet is, how to use it, source analysis, and summary.