Junior Developer 路 1-2 years
Junior interviews move from definitions to application. Expect to be asked how you would use a feature in real code, what goes wrong when you misuse it and how you would debug it.
91 questions
Specificity is the score the browser uses to decide which rule wins: inline styles beat IDs, IDs beat classes/attributes/pseudo-classes, and those beat elements. When scores tie, the last rule in the source wins.
any turns off checking. unknown is a type-safe any: you must narrow it before use. never means a value cannot exist, used for exhaustive checks and functions that always throw.
Generics are type parameters: they let a function, class or type work with many types while keeping the relationship between inputs and outputs, instead of falling back to any.
A union (A | B) is a value that is one of the members. An intersection (A & B) is a value that must satisfy both types at once.
Utility types are built-in helpers that transform an existing type: Partial makes every field optional, Required the opposite, Pick keeps a set of keys, Omit removes them, and Record builds a key/value map.
Use a subquery that takes the MAX salary below the overall MAX, or use DENSE_RANK() and pick rank 2, which also handles ties and generalises to the Nth highest.
Find duplicates with GROUP BY and HAVING COUNT(*) > 1, then delete them by numbering rows within each duplicate group with ROW_NUMBER() and removing every row after the first.
Normalization is organising tables to reduce redundancy and update anomalies: 1NF means atomic values, 2NF removes partial dependencies on part of a composite key, and 3NF removes dependencies between non-key columns.
An abstract class can hold state, constructors and partial implementation but a class can inherit only one, while an interface defines a contract that a class can implement many of.
Boxing converts a value type to object by allocating it on the heap, and unboxing converts it back; both add allocations and casts, so avoid them in hot code paths.
LINQ (Language Integrated Query) lets you query collections, databases and XML with a consistent syntax, and deferred execution means a query does not run when you define it but when you enumerate the results.
An abstract class can have instance fields, constructors and a mix of implemented and abstract methods but supports only single inheritance, while an interface defines a contract that a class can implement multiple times and, since Java 8, can include default methods.
ArrayList is backed by a resizable array with O(1) index access and O(n) insertion in the middle, while LinkedList is a doubly linked list with O(n) index access and O(1) insertion once you hold the node; in practice ArrayList is faster for most workloads.
Checked exceptions (subclasses of Exception other than RuntimeException) must be caught or declared with throws, while unchecked exceptions (RuntimeException and Error) do not have to be handled and usually signal programming bugs.
Java 8 introduced lambda expressions, functional interfaces, the Stream API for declarative collection processing, Optional to represent missing values, default methods in interfaces, method references and the java.time date and time API.
Default argument values are evaluated once when the function is defined, so a default list or dictionary is shared between every call that does not pass its own, causing data to leak between calls.
A shallow copy creates a new container but reuses the same nested objects, while a deep copy recursively copies everything so the new object is fully independent.
A classmethod receives the class as its first argument (cls) and can create or configure instances, while a staticmethod receives no automatic argument and is just a function placed inside the class namespace.
A load balancer distributes incoming requests across several servers to improve capacity and availability, using algorithms such as round robin, least connections or consistent hashing.
Both integrate changes from one branch into another: merge keeps both histories and joins them with a merge commit, while rebase rewrites your commits so they appear on top of the target branch, giving a linear history.