使用記錄（record）當(dāng)數(shù)據(jù)是不可變的、僅用於承載數(shù)據(jù)且無復(fù)雜行為；2. 使用類（class）當(dāng)需要封裝、可變狀態(tài)、繼承或驗(yàn)證邏輯；3. 避免在記錄中添加實(shí)例字段或破壞不可變性；4. 記錄適用於DTO、返回值封裝，類適用於包含業(yè)務(wù)邏輯或生命週期管理的場(chǎng)景；5. 若對(duì)象僅為數(shù)據(jù)聚合，用記錄，若為有行為的對(duì)象，用類。

In Java, choosing between records and classes comes down to understanding the intent behind your data structure. Since records were introduced in Java 16 (as a permanent feature), they've provided a concise way to model immutable data carriers—but they're not a replacement for classes in every scenario. Here's when to use each, based on practical design patterns and real-world usage.

? Use Records for Immutable Data Carriers

Records are ideal when you're modeling data that:

• Is immutable
• Has no behavior (or minimal behavior)
• Exists primarily to hold and transfer data

A record automatically generates:

• A constructor for all fields
• equals() , hashCode() , and toString() methods
• Accessor methods (getters) for each field

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

This single line replaces what would be 20 lines in a traditional class.

When to use:

• DTOs (Data Transfer Objects)
• POJOs with only fields and getters
• Method return types bundling multiple values
• Keys in maps or configurations

? If you find yourself writing a class that only holds data and doesn't have mutable state or complex logic, it's likely a perfect candidate for a record.

? Use Classes When You Need Behavior or State Control

Classes remain the right choice when you need:

• Encapsulation (private fields with controlled access)
• Mutable state
• Inheritance (though use sparingly)
• Validation logic in constructors/setters
• Lazy initialization or computed fields
• Multiple constructors with different logic

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

    public Person(String name, int age) {
        if (age < 0) throw new IllegalArgumentException("Age cannot be negative");
        this.name = name;
        this.age = age;
    }

    public boolean isAdult() {
        return age >= 18;
    }

    // Getters, maybe setters if mutable
}

When to use classes:

• Domain models with business logic
• Entities that evolve over time
• Objects requiring lifecycle management
• Cases where you need to hide internal representation

? Records can't have instance fields beyond the header, can't extend other classes, and are final by design—so they're inflexible for complex modeling.

? Don't Force Records Where They Don't Fit

Some anti-patterns to avoid:

• Adding mutators to records

   public record Person(String name, int age) {
      private String email; // ? Instance field not allowed
      public void setEmail(String email) { this.email = email; } // ? Breaks immutability
  }

• Using records for configuration with logic
  If your "config" object validates inputs or changes behavior based on state, use a class.

• Overriding accessors just to add logic
  You can override accessors in records, but doing so often signals you should use a class instead.

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? Best Practices Summary

Scenario	Use
Pure data, immutable, transparent	? Record
Need validation or side effects	? Class
Want inheritance or polymorphism	? Class
Bundling return values from a method	? Record
Frequent copying with with -style methods	? Record (no built-in with )
Need lazy-computed or derived fields	? Class

?? Note: Records don't support with methods like Kotlin's data classes. If you need copy-and-modify patterns, a builder pattern in a class may be better.

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Final Thoughts

Think of records as "data, not behavior" . They're not meant to replace classes but to eliminate boilerplate when you're modeling simple, immutable aggregates.

Use records when:

• You're tired of writing boilerplate for DTOs
• The object's entire meaning is its data

Use classes when:

• You need encapsulation, behavior, or lifecycle control
• Your model evolves or enforces invariants

Choosing correctly leads to cleaner, more maintainable code. When in doubt, start with a record—if you need more control, refactor to a class. It's a safe evolution path.

Basically: if it's a bag of data, use a record. If it's an object with purpose, use a class.

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