All notes, in reading order - Page 4

An enum is a class with a fixed set of instances, which makes an invalid value impossible rather than merely unlikely.

A record declares an immutable data carrier, and the compiler generates the constructor, accessors, equals, hashCode and toString.

Java

An annotation attaches metadata to code. It changes nothing by itself; a compiler, a tool or a framework reads it and acts.

Java

Wrapper classes turn primitives into objects so they can be used with generics and collections, and the conversion is automatic but not free.

Java

Errors, checked exceptions and unchecked exceptions sit in one hierarchy, and knowing which is which decides how you should react.

Java

try guards a block, catch handles specific failures, finally always runs, and try with resources closes what you opened.

Java

throw raises an exception now; throws declares that a method may raise one and leaves the handling to the caller.

Java

A custom exception names a failure in the language of your domain, which makes handling precise and messages meaningful.

Java

The rules that separate exception handling which helps from exception handling which hides bugs.

Java

A small set of interfaces describes how groups of objects behave, and many implementations trade memory, ordering and speed differently.

Java

A List keeps insertion order and allows duplicates. ArrayList is the default; LinkedList wins only at the ends.

Java

A Set stores unique elements. The three implementations differ in ordering and in what uniqueness is based on.