java - 使用多个属性对对象列表进行分组

Question

如何使用 Java 中的多个属性对对象列表进行分组？如果我有包含州代码、部门、分支机构、金额、帐户的财务详细信息列表。现在我想添加具有相同州代码、Dept、Branch、Amount、AccountCode的金额.

    FinancialDetails f1 = new FinancialDetails("01","005","test1",12.23D,"12345");
    FinancialDetails f2 = new FinancialDetails("01","005","test1",123.23D,"12345");
    FinancialDetails f3 = new FinancialDetails("01","005","test1",99.23D,"12345");
    FinancialDetails f4 = new FinancialDetails("02","006","test1",123.23D,"89898");
    FinancialDetails f5 = new FinancialDetails("02","006","test1",125.23D,"89898");
    FinancialDetails f6 = new FinancialDetails("03","020","test2",625.23D,"89898");
    List<FinancialDetails> list = new ArrayList<FinancialDetails>();
    list.add(f1);
    list.add(f2);
    list.add(f3);
    list.add(f4);
    list.add(f5);
    list.add(f6);

现在我想通过添加具有相同状态代码、部门、分支机构、帐户的金额来创建一个对象

Answer 1

尝试:

private static class Key {
    String stateCode;
    String dept;
    // ...
    // + hashcode equals
}
public Collection<List<FinancialDetails>> group(List<FinancialDetails> original) {
    Map<Key, List<FinancialDetails>> groupingMap = new HashMap<>();
    for(FinancialDetails fd : original) {
        Key key = new Key(fd.getStateCode, fd.getDept); // ...
        List<FinancialDetails> group = groupingMap.get(key);
        if(group == null) {
            group = new ArrayList<>();
            groupingMap.put(key, group);
        }
        group.add(fd);
    }
    return groupingMap.values();
}