A representation class to communicate to Open Exchange Rates API

CurrencyData.java

public class CurrencyData {

    /**
     * A string with a disclaimer.
     */
    private String disclaimer;
    /**
     * A string with a license.
     */
    private String license;
    /**
     * A timestamp.
     */
    private long timestamp;
    /**
     * The currency relative to which exchange rates are returned. In a free
     * version of the API one cannot change the base and it is US Dollar by
     * default.
     */
    private String base;
    /**
     * A map with exchange rate with keys like USD for US Dollar, EUR for Euro,
     * CAD for Canadian Dollar etc.
     */
    private Map<String, Double> rates = new HashMap<>();

    /**
     * A no-argument constructor.
     */
    public CurrencyData() {
    }

    /**
     * A constructor needed for testing.
     *
     * @param disclaimer A string with a disclaimer.
     * @param license A string with a license.
     * @param timestamp A timestamp.
     * @param base The currency relative to which exchange rates are returned.
     */
    public CurrencyData(String disclaimer, String license, long timestamp, String base) {
        this.disclaimer = disclaimer;
        this.license = license;
        this.timestamp = timestamp;
        this.base = base;
    }

    //Getters and setters.
    ...

}