Zone.java

import java.util.Objects;

public class Zone {
    private String name;

    public Zone(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "Zone " + name;
    }

    @Override
    public boolean equals(Object o) {
        return o instanceof Zone && Objects.equals(((Zone) o).name, this.name);
    }

    @Override
    public int hashCode() {
        return name.hashCode();
    }
}