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Java Records, introduced as a preview feature in Java 14 and finalized in Java 16, offer a concise way to create immutable data classes. Records drastically reduce boilerplate code and are ideal for modeling data without behavior.

1. What Are Records in Java?

A record is a special kind of class in Java that automatically provides:

• A constructor
• getters for all fields
• equals(), hashCode(), and toString() implementations

This makes records ideal for simple data carriers or value objects.

2. Basic Syntax

java

public record Person(String name, int age) {}

This is equivalent to:

java

public final class Person {
    private final String name;
    private final int age;

    public Person(String name, int age) { ... }
    public String name() { return name; }
    public int age() { return age; }
    public boolean equals(Object o) { ... }
    public int hashCode() { ... }
    public String toString() { ... }
}

3. Key Characteristics

• Immutable by default
• Final by design — you can’t extend a record
• Implements java.lang.Record implicitly
• Fields are implicitly private final
• Compact constructor customization is allowed

4. Customizing Constructors and Methods

You can add validation logic:

java

public record Product(String name, double price) {
    public Product {
        if (price < 0) throw new IllegalArgumentException("Price must be positive");
    }
}

Add additional methods if needed:

java

public String displayLabel() {
    return name + " - $" + price;
}

5. Records vs Traditional POJOs

FeaturePOJORecordSyntaxVerboseConciseMutabilityMutable by defaultImmutableInheritanceCan be extendedCannot be extendedBoilerplateHighMinimalIdeal Use CaseFull-featured objectsSimple data carriers

6. Use Cases for Records

• DTOs (Data Transfer Objects)
• API responses and requests
• Configuration objects
• Keys in maps (due to built-in equals() and hashCode())

7. Limitations of Records

• Cannot extend other classes
• Cannot define mutable fields
• Not suitable for entities with changing state
• Less flexible for complex business logic

8. Records and Serialization

Records are serializable, and frameworks like Jackson and Gson support them with proper configuration. Make sure to use default constructors or annotations depending on the library.

Java Records are a modern, elegant feature for clean data modeling. They encourage immutability, reduce boilerplate, and promote a more functional programming style in Java.