Question

我正在尝试构建一个树形图，并为键类实现了我自己的Comparable接口，但我仍然得到一个“无法转换为可比较的”异常，我真的不明白为什么。这是我的代码的相关部分：

接口：

public interface Comparable<T> {

public int compareTo(T o);

}

密钥类：

public class PriorityBuy implements Comparable<PriorityBuy>{

protected double _priceDouble;
protected DollarValue _priceDollarValue = new DollarValue(_priceDouble);
protected Price _price = new Price(_priceDollarValue);
protected long _time;

public PriorityBuy(Price price, long time) {

    this._price = price;
    this._time = time;

}

public Price getPrice() {
    return _price;
}

public long getTime() {
    return _time;
}

/**
 * The following provides a new choice of hash function for this class.  The reason is that
 * we need to create a new equals method to match the compareTo method, and we need to know
 * that equal objects return equal hashCode.
 */

@Override
public int hashCode() {
    return (int) (((_price.hashCode())*13)^(_time));
}

/**
 * We re-implement the equals method to match our compareTo method, which depends on both price
 * and on time.
 */

@Override
public boolean equals(Object o) {
    if(! (o instanceof PriorityBuy)) {
        return false;
    }
    PriorityBuy p = (PriorityBuy) o;
    if(p.getPrice().getDollarValue().getValue() == _price.getDollarValue().getValue() && p.getTime() == _time) {
        return true;
    }

    return false;
}

/**
 * We are writing a compareTo method so that this class can implement Comparable<Priority>, which
 * in turn allows any treemap constructed with Priority as the class of keys to order the tree
 * according to the ordering defined by the compareTo method defined below, instead of using
 * the "natural ordering" as it usually does.
 */

@Override
public int compareTo(PriorityBuy a) {

    if(a.getPrice().getDollarValue().getValue() > this.getPrice().getDollarValue().getValue()) {
        return -1;
    }
    else if(a.getPrice().getDollarValue().getValue() < this.getPrice().getDollarValue().getValue()) {
        return 1;
    }
    else if(a.getTime() < this.getTime()) {
        return -1;
    }
    else if(a.getTime() > this.getTime()) {
        return 1;
    }
    else {
        return 0;   
    }
}


}

我在树中添加元素的部分：

public void addToBuyBook(OrderBookMessage obm) throws Exception {
    Order order = this.createOrder(obm);
    TreeMap<PriorityBuy,Order> buyBookTree = _buyBook.get(obm.getTicker());
    buyBookTree.put(order.getPriorityBuy(), order);
    _buyBook.put(obm.getTicker(), buyBookTree);
    this.addBuyOrder(obm.getOrderID(), obm.getTicker(), obm.getLimitPrice(), obm.getQuantity());
}

现在，当我使用测试来测试此代码时：

public void testAddToBuyBook() throws Exception {
    OrderBookManager manager = new OrderBookManager();
    OrderBookMessage obm1 = new OrderBookMessage("IBM");
    OrderBookMessage obm2 = new OrderBookMessage("IBM");

    manager.addToBuyBook(obm1);

    manager.addToBuyBook(obm2);


}

然后它返回异常，即PriorityBuy无法解析为可比较。但似乎我已经构建了程序，以便这应该工作。所以......任何人都可以帮我看看它为什么不是吗？

Answer 1

您无法创建自己的Comparable界面;您必须使用内置java.lang.Comparable。

可比较的<t>不适用于treemap </t>

1 个答案: