java - 如何对HashSet()函数数据按顺序排序？

Question

我是 Java 新手，我想要执行的功能是将文件中的一系列数据加载到我的 hashSet() 函数中。

问题是，我可以按顺序输入所有数据，但无法根据文件中的帐户名按顺序检索出来。

有人可以帮忙吗？

下面是我的代码:

公共(public)设置检索历史记录(){ 设置数据组 = new HashSet(); 尝试{

        File file = new File("C:\\Documents and Settings\\vincent\\My Documents\\NetBeansProjects\\vincenttesting\\src\\vincenttesting\\vincenthistory.txt");

        BufferedReader br = new BufferedReader(new FileReader(file));
        String data = br.readLine();
        while(data != null){
            System.out.println("This is all the record:"+data);
            Customer cust = new Customer();
            //break the data based on the ,
            String array[] = data.split(",");
            cust.setCustomerName(array[0]);
            cust.setpassword(array[1]);
            cust.setlocation(array[2]);
            cust.setday(array[3]);
            cust.setmonth(array[4]);
            cust.setyear(array[5]);
            cust.setAmount(Double.parseDouble(array[6]));
            cust.settransaction(Double.parseDouble(array[7]));
            dataGroup.add(cust);
            //then proced to read next customer.

            data = br.readLine();
        } 
        br.close();
    }catch(Exception e){
        System.out.println("error" +e);
    }
    return dataGroup;
}

public static void main(String[] args) {
    FileReadDataModel fr = new FileReadDataModel();
    Set customerGroup = fr.retrieveHistory();
  System.out.println(e);
    for(Object obj : customerGroup){
        Customer cust = (Customer)obj;

        System.out.println("Cust name :" +cust.getCustomerName());
        System.out.println("Cust amount :" +cust.getAmount());

    }

Answer 1

直接来自HashSet javadoc 类

This class implements the Set interface, backed by a hash table (actually a HashMap instance). It makes no guarantees as to the iteration order of the set; in particular, it does not guarantee that the order will remain constant over time. This class permits the null element.

如果您使用此类，则无法保证顺序。为此，您将需要引入另一种数据结构。如ArrayList或LinkedHashSet .