Java Records Cheat Sheet

Covers Java record syntax, compact constructors, added methods, record pattern matching, and key immutability rules for data carriers.

2 PagesIntermediateApr 2, 2026

Declaring a Record

A record is an immutable data carrier with auto-generated boilerplate.

java

// Implicitly final, implements equals(), hashCode(), toString(), and accessorspublic record Point(int x, int y) {}Point p = new Point(3, 4);System.out.println(p.x());       // 3 (accessor, not getX())System.out.println(p);           // Point[x=3, y=4]System.out.println(p.equals(new Point(3, 4)));  // true

Compact Constructor

Validate or normalize fields without repeating the parameter list.

java

public record Range(int min, int max) {    // Compact constructor: no parameter list, fields are implicitly assigned after    public Range {        if (min > max) {            throw new IllegalArgumentException("min must be <= max");        }    }}new Range(5, 1);  // throws IllegalArgumentException

Adding Methods & Static Members

Records can declare extra instance methods, static fields, and static factories.

java

public record Point(int x, int y) {    static final Point ORIGIN = new Point(0, 0);    double distanceToOrigin() {        return Math.sqrt(x * x + y * y);    }    static Point of(int x, int y) {        return new Point(x, y);    }}

Record Patterns (Java 21+)

Deconstruct records in switch and instanceof for concise pattern matching.

java

Object obj = new Point(1, 2);if (obj instanceof Point(int x, int y)) {    System.out.println(x + y);}String label = switch (obj) {    case Point(int x, int y) when x == 0 && y == 0 -> "origin";    case Point(int x, int y) -> "point at " + x + "," + y;    default -> "unknown";};

Key Facts

Rules and restrictions that define record behavior.

Immutability- All fields are implicitly private and final; no setters are generated.
Canonical Constructor- Auto-generated constructor matching the component list unless a compact or explicit one is defined.
Accessors- Generated accessor methods are named after the field, not getX() - e.g. x() not getX().
No Extra Instance Fields- Records cannot declare additional non-static instance fields beyond their components.
Implicit final- A record class is implicitly final and cannot be extended.
Can Implement Interfaces- Records can implement interfaces but cannot extend another class (they implicitly extend java.lang.Record).

Pro Tip

Use records for DTOs and immutable value objects, but keep JPA/Hibernate entities as regular classes - records' lack of a mutable state and final fields conflicts with how JPA proxies and lazy loading work.

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