Can generating a large number of methods in a data class negatively affect the application's performance or other aspects?

Yes, possibly, especially when using certain ProGuard/R8 settings.

• APK size: Each generated method in a data class (equals(), hashCode(), toString(), copy()) increases the bytecode size, which directly affects the APK size.
• Compilation speed: A large number of methods requiring processing by the compiler (including ProGuard/R8 optimizations) can slightly increase compilation time.
• ProGuard/R8 performance: With aggressive ProGuard/R8 settings (e.g., obfuscation, optimization), a large number of generated methods can increase processing time for these tools. In rare cases, false positives in optimizations may occur with very complex call graphs.
• Limit of 65,536 methods (Dex Limit): Although this limit is more relevant to the total number of methods in the app, a large number of data classes with generated methods contribute to this limit.

In most typical scenarios on modern devices, the impact of these factors is minimal. However, with a large number of data classes with many fields, or strict requirements on APK size and build time, these aspects can become more noticeable.

Example:

// Example data class
data class User(
    val id: Long,
    val name: String,
    val email: String,
    val birthday: String?,
    val registrationDate: String,
    val lastLoginDate: String?,
    val status: String,
    val isActive: Boolean,
    val address: String,
    val city: String,
    val zipCode: String,
    val страна: String
    // ... many fields
)
// This data class generates equals, hashCode, toString, copy,
// each of which processes all fields.
// The more fields, the more complex (and potentially longer) the execution of these methods.