JAVA 21

Records

Records are a new kind of type declaration in Java. They are a special kind of class that holds pure data. A record
automatically has a final field for each component, a public constructor, and public read accessor methods.

public record Point(int x, int y) {}

What this concise syntax is providing is:

• A concise syntax for the constructor declaration
• A private final field for each component
• A public read accessor method for each component e.g:

Point p = new Point(1, 2);
System.out.println(p.x()); // 1
System.out.println(p.y()); // 2

• An implicit public equals method that compares the fields of two records
• An implicit public hashCode method that uses the fields of the record to compute the hash code
• An implicit public toString method that returns a string representation of the record

Prove

• Record patterns and destructuring in instanceof
• Record patterns and destructuring in switch
• Switch expressions with records
• Exhaustiveness checking with switch expressions
• Sealed classes and interfaces
• Switch with guarded patterns
• Switch handling null

Questions

• Why use pattern matching over inheritance and method overriding in the balance use case?

Use cases

• Use when you do not own the class hierarchy in which implement method overrides