User.java

public final class User {
    @NotNull
    private final String email;
    private final int age;

    public User(@NotNull String email, int age) {
        if (email == null) {
            throw new RuntimeException("Email can't be null");
        }
        this.email = email;
        this.age = age;
    }

    @NotNull
    public final String getEmail() {
        return this.email;
    }

    public final int getAge() {
        return this.age;
    }

    public String toString() {
        return "User(email=" + this.email + ", age=" + this.age + ")";
    }

    public int hashCode() {
        return (this.email != null ? this.email.hashCode() : 0) * 31 + this.age;
    }

    @NotNull
    public final User copy(@NotNull String email, int age) {
        Intrinsics.checkParameterIsNotNull(email, "email");
        return new User(email, age);
    }

    public boolean equals(Object otherObject) {
        if (this != otherObject) {
            if (otherObject instanceof User) {
                User otherUser = (User) otherObject;
                if (this.email.equals(otherUser.email) && this.age == otherUser.age) {
                    return true;
                }
            }
            return false;
        } else {
            return true;
        }
    }
}