Java集合排序BigDecimal

Question

我正试着用ArrayList来分类BigDecimal，然后碰到一块砖墙。我有一门课看起来有点像这样：

public class deal implements Comparable<deal>{

protected BigDecimal bdPrice;
protected int iQuantity;
protected String sDealType;
protected UUID dealUniqueID;
protected int dealID;
protected BigDecimal bdUnitPrice;

public deal(){
    bdPrice         = new BigDecimal("0");
    bdUnitPrice     = new BigDecimal("0");
    iQuantity       = 1;
    sDealType       = "Single item";
    dealUniqueID    = UUID.randomUUID();
    dealID          = 0;
}

private void setUnitPrice(){
    this.bdUnitPrice = this.bdPrice.divide(new BigDecimal(this.iQuantity));
}

public BigDecimal compareTo(deal oDeal) {
    // TODO Auto-generated method stub
    return bdUnitPrice.compareTo(oDeal.getUnitPrice());
}

public boolean equals(deal oDeal) {
    if (!(oDeal instanceof deal))
        return false;
    deal oD = (deal) oDeal;

    return this.bdUnitPrice.equals(oD.bdUnitPrice);
}
}

我主要的Android活动是这样的：

public class SupermarketDealsActivity extends Activity {
private ArrayAdapter<deal> itemAdapter;
private ListView lvDeals;
private ArrayList<deal> itemArray;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    SetUpView();
}

private void SetUpView(){
lvDeals                     = (ListView)this.findViewById(R.id.listDeals);

    itemArray                   = new ArrayList<deal>();
    itemArray.clear();

    itemAdapter                 = new ArrayAdapter<deal>(this, android.R.layout.simple_list_item_1,itemArray);
    lvDeals.setAdapter(itemAdapter);
}

private void CreateADeal(int iQuantity, BigDecimal bdPrice) {
    deal oDeal                  = new deal();

    oDeal.setQuantity(iQuantity);
    oDeal.setPrice(bdPrice);

    CreateListDeals(oDeal);
}

private void CreateListDeals(deal oDeal){
    itemArray.add(oDeal);
    Collections.sort(itemArray,Collections.reverseOrder());
    itemAdapter.notifyDataSetChanged();
}
}

在我的java类中，我的compareTo方法出现了一个错误，它说：

类型不匹配:无法从int转换为BigDecimal

我一定是在路上错过了什么，是什么？

干杯

Answer 1

public BigDecimal compareTo(deal oDeal) {
    // TODO Auto-generated method stub
    return bdUnitPrice.compareTo(oDeal.getUnitPrice());
}

既不匹配接口的签名，也不匹配bdUnitPrice.compareTo的返回类型。改为：

public int compareTo(deal oDeal) {
    // TODO Auto-generated method stub
    return bdUnitPrice.compareTo(oDeal.getUnitPrice());
}

我还应该提几点(从评论中)：

1. 类的名称应该以大写字母开头。有一个"代码约定“文档详细说明了这一点和其他你应该做的事情。
2. 重写equals --除非也重写hashCode，否则永远不应该重写hashCode--否则，如果将该类的对象放入使用哈希的HashSet、HashMap或其他集合中，就会出现大量问题。