public final class Key implements Serializable {
    static final long serialVersionUID = -448150158203091507L;
    public final String targetClassName;
    public final String id;
    public final String toString;
    public final int hashCode;

    public Key() {
        targetClassName = null;
        id = null;
        toString = null;
        hashCode = -1;
    }

    public Key(String str) {
        String[] parts = str.split("\\(");
        parts[1] = parts[1].replaceAll("\\)", " ");
        parts[1] = parts[1].replace("\"", " ");
        parts[1] = parts[1].trim();
        this.targetClassName = parts[0];
        this.id = parts[1];
        toString = this.toString();
        hashCode = this.hashCode();
    }

    public Key(String classCollectionName, String id) {
        if (StringUtils.isEmpty(classCollectionName)) {
            throw new IllegalArgumentException("No collection/class name specified.");
        }
        if (id == null) {
            throw new IllegalArgumentException("ID cannot be null");
        }
        targetClassName = classCollectionName;
        this.id = id;
        toString = this.toString();
        hashCode = this.hashCode();
    }

    public String getTargetClassName() {
        return targetClassName;
    }

    public int hashCode() {
        if(hashCode != -1) return hashCode; 
        int prime = 31;
        int result = 1;
        result = prime * result + (id != null ? id.hashCode() : 0);
        result = prime * result + (targetClassName != null ? targetClassName.hashCode() : 0);
        return result;
    }

    public boolean equals(Object object) {
    if (object instanceof Key) {
        Key key = (Key) object;
        if (this == key)
            return true;
        return targetClassName.equals(key.targetClassName) && Objects.equals(id, key.id);
    } else {
        return false;
    }
}

    public String toString() {
        if(toString != null) return toString;
        StringBuilder buffer = new StringBuilder();
        buffer.append(targetClassName);
         buffer.append("(");
        if (id != null) {
            buffer.append((new StringBuilder()).append("\"").append(id)
                    .append("\"").toString());
        } else {
            buffer.append("no-id-yet");
        }
        buffer.append(")");
        return buffer.toString();
    }

}

@PersistenceCapable(detachable="true")
@Inheritance(strategy=InheritanceStrategy.COMPLETE_TABLE)
public class Ticket implements Entity {

    @PrimaryKey
    @Persistent(valueStrategy = IdGeneratorStrategy.UNSPECIFIED, column="_id")
    protected Key key;

    protected String date;
    protected int qty;

    public Ticket() {
        this.qty = 0;
    }

    public Key getKey() {
        return key;
    }

    @Override
    public void setKey(Key key) {
        this.key = key;
    }

    public double getQty() {
        return qty;
    }

    public void setQty(double qty) {
        this.qty = (int) qty;
    }

    public String getDate() {
        return date;
    }

    public void setDate(String date) {
        this.date = date;
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((key == null) ? 0 : key.hashCode());
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Ticket other = (Ticket) obj;
        if (key == null) {
            if (other.key != null)
                return false;
        } else if (!key.equals(other.key))
            return false;
        return true;
    }

    @Override
    public String toString() {
        return "Ticket [key=" + key + ", date=" + date + ", qty="
                + qty + "]";
    }

}