What methods can you name for verifying data correctness?

The main methods of data validation include:

• Format validation — checking that data conforms to the expected format (e.g., email, phone, date).
• Range checks — numerical values should fall within an acceptable range.
• Required fields check — ensuring all necessary data is filled.
• Uniqueness check — for example, a unique login or identifier.
• Cross-field validation — consistency between different fields (e.g., start date not later than end date).
• Null check — to avoid NullPointerException.
• Regular expressions — for complex pattern validation.
• Business logic validation — for example, access rights or domain restrictions.

In Java, these are often implemented using:

• Built-in checks in code (if-conditions).
• Annotations from the Bean Validation API (e.g., @NotNull, @Size, @Pattern) along with implementations like Hibernate Validator.

Example with Bean Validation:

public class User {
    @NotNull
    @Size(min = 2, max = 30)
    private String name;

    @Email
    private String email;

    // getters and setters
}

This allows for centralized and declarative data validation rules.