我正在尝试按 BigDecimal 对 ArrayList 进行排序,但遇到了障碍。我有一个看起来有点像这样的类:
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);
}
}
我的主要 Android Activity 如下所示:
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 方法出现错误:
Type mismatch: cannot convert from int to BigDecimal
我一定是错过了什么,那是什么?
干杯
最佳答案
public BigDecimal compareTo(deal oDeal) {
// TODO Auto-generated method stub
return bdUnitPrice.compareTo(oDeal.getUnitPrice());
}
既不匹配接口(interface)的签名,也不匹配 bdUnitPrice.compareTo
的返回类型。将其更改为:
public int compareTo(deal oDeal) {
// TODO Auto-generated method stub
return bdUnitPrice.compareTo(oDeal.getUnitPrice());
}
我应该提到的其他一些事情(来自评论):
- 类名应以大写字母开头。有一个“code conventions”文档,其中详细说明了您应该做的事情和其他事情。
- 你重写
equals
- 你不应该重写equals
除非你也重写hashCode
- 否则你会遇到很多问题,如果你把将此类的对象转换为 HashSet、HashMap 或其他使用散列的集合。
关于Java 集合排序 BigDecimal,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/11254521/