User Classes

JUser.java

import java.util.Objects;

public final class JUser {

    private static final int DEFAULT_AGE = 1;
    private static final String DEFAULT_MIDDLE = "";

    // start fields

    private int age;
    @Nonnull
    private String firstName, middleName, lastName;


    // start constructors (many permutations more due to parameter labels)

    public JUser(@Nonnull String firstName, @Nonnull String middleName, @Nonnull String lastName, int age) {
        assert firstName != null;
        assert middleName != null;
        assert lastName != null;
        this.age = age;
        this.firstName = firstName;
        this.middleName = middleName;
        this.lastName = lastName;
    }

    public JUser(@Nonnull String firstName,@Nonnull String middleName, @Nonnull String lastName) {
        this(firstName, middleName, lastName, DEFAULT_AGE);
    }

    public JUser(@Nonnull String firstName, @Nonnull String lastName, int age) {
        this(firstName, DEFAULT_MIDDLE, lastName, age);
    }

    public JUser(@Nonnull String firstName, @Nonnull String lastName) {
        this(firstName, lastName, DEFAULT_AGE);
    }


    // start getters/setters
    
    @Nonnull
    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(@Nonnull String firstName) {
        assert firstName != null;
        this.firstName = firstName;
    }

    @Nonnull
    public String getMiddleName() {
        return middleName;
    }

    public void setMiddleName(@Nonnull String middleName) {
        assert middleName != null;
        this.middleName = middleName;
    }

    @Nonnull
    public String getLastName() {
        return lastName;
    }

    public void setLastName(@Nonnull String lastName) {
        assert lastName != null;
        this.lastName = lastName;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }


    // start components

    @Nonnull
    public String component1() {
        return firstName;
    }

    @Nonnull
    public String component2() {
        return middleName;
    }

    @Nonnull
    public String component3() {
        return lastName;
    }

    public int component4() {
        return age;
    }


    // start copy (many permutations more due to parameter labels)

    @Nonnull
    public JUser copy(@Nonnull String firstName, @Nonnull String middleName, @Nonnull String lastName, int age) {
        assert firstName != null;
        assert middleName != null;
        assert lastName != null;
        return new JUser(firstName, middleName, lastName, age);
    }

    @Nonnull
    public JUser copy(@Nonnull String firstName, @Nonnull String middleName, @Nonnull String lastName) {
        return copy(firstName, middleName, lastName, this.age);
    }

    @Nonnull
    public JUser copy(@Nonnull String firstName, @Nonnull String middleName) {
        return copy(firstName, middleName, this.lastName, this.age);
    }

    @Nonnull
    public JUser copy(@Nonnull String firstName) {
        return copy(firstName, this.middleName, this.lastName, this.age);
    }

    @Nonnull
    public JUser copy() {
        return copy(this.firstName, this.middleName, this.lastName, this.age);
    }


    // start object overrides

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (!(o instanceof JUser)) return false;
        JUser jUser = (JUser) o;
        return getAge() == jUser.getAge() &&
               Objects.equals(getFirstName(), jUser.getFirstName()) &&
               Objects.equals(getMiddleName(), jUser.getMiddleName()) &&
               Objects.equals(getLastName(), jUser.getLastName());
    }

    @Override
    public int hashCode() {
        return Objects.hash(getAge(), getFirstName(), getMiddleName(), getLastName());
    }

    @Override
    public String toString() {
        final StringBuilder sb = new StringBuilder("JUser{");
        sb.append("age=").append(age);
        sb.append(", firstName='").append(firstName).append('\'');
        sb.append(", middleName='").append(middleName).append('\'');
        sb.append(", lastName='").append(lastName).append('\'');
        sb.append('}');
        return sb.toString();
    }

}

KUser.kt

data class KUser(var firstName : String, var middleName : String = "", var lastName : String, var age : Int = 1)

RUser.rs

#[derive(Copy, Clone, Debug)]
struct RUser {
  pub firstName: String,
  pub middleName: String,
  pub lastName: String,
  pub age: u32
}