java - 如何根据某些特定值对 map 中的值进行分组？

Question

我有来自 map 的值，如下所示

Key = 1_1, Value = 02/04/2012
Key = 1_2, Value = 03/04/2012
Key = 1_3, Value = 04/04/2012
Key = 1_4, Value = 05/04/2012
Key = 1_5, Value = 06/04/2012
Key = 1_6, Value = 09/04/2012
Key = 1_7, Value = 10/04/2012
Key = 1_8, Value = 11/04/2012
Key = 1_9, Value = 12/04/2012
Key = 1_10, Value = 13/04/2012
Key = 1_11, Value = 18/04/2012
Key = 1_12, Value = 19/04/2012
Key = 1_13, Value = 20/04/2012
Key = 1_14, Value = 23/04/2012
Key = 1_15, Value = 24/04/2012
Key = 1_16, Value = 25/04/2012
Key = 1_17, Value = 26/04/2012
Key = 1_18, Value = 27/04/2012
Key = 1_19, Value = 30/04/2012
Key = 10_20, Value = 02/04/2012
Key = 10_21, Value = 03/04/2012
Key = 10_22, Value = 04/04/2012
Key = 10_23, Value = 05/04/2012
Key = 10_24, Value = 06/04/2012
Key = 10_25, Value = 09/04/2012
Key = 10_26, Value = 10/04/2012
Key = 10_27, Value = 11/04/2012
Key = 10_28, Value = 12/04/2012
Key = 10_29, Value = 13/04/2012
Key = 10_30, Value = 16/04/2012
Key = 10_31, Value = 17/04/2012
Key = 10_32, Value = 18/04/2012
Key = 10_33, Value = 19/04/2012
Key = 10_34, Value = 23/04/2012
Key = 10_35, Value = 24/04/2012
Key = 10_36, Value = 26/04/2012
Key = 10_37, Value = 27/04/2012

我真的很难将这些值分开并将它们放入单独的 map 中。

我想按如下方式分组。

1_1 到 1_19 我想根据“_”进行分割并单独获取第一个值并将它们分组到一个单独的 map 中。

例如 1 是键，值是日期。

编辑:

employeeMap =  showExelData(sheetData);
        String previousEemployeeID = "",employeeID[];
        Iterator<Map.Entry> entries = employeeMap.entrySet().iterator();
        while (entries.hasNext()) {
            Map.Entry entry = entries.next();
            employeeID = entry.getKey().toString().split("_");

                // this is the place where i want to check the values if 1 than group the values it can be even  Key = 1_0, Value = 25/04/2012 to  If Key = 1_18, Value = 30/04/2012
     but when the other one comes ex :  Key = 10_0, Value = 25/04/2012 to  If Key = 10_17, Value = 30/04/2012it has to go to new Map 

这就是我欠缺的地方。 }

Answer 1

如果要将 1_1、1_2 拆分为 1_19..，请使用 String 类的 split() 函数。

例如。

String x = 1_19;

String[] y = x.split("_");

y[0] 等于 1，y[1] 等于 19

至于使用 map 中键的第一个值，这是不可能的，因为它需要 map 中的每个条目都有一个唯一的键，就像 npinti 在您的帖子中评论的那样。

public class Mapping {

    Map<String, String> coMap;
    List<String> coList;

    public Mapping() 
    {
        init();
    }

    public static void main(String[] args) 
    {
        Mapping oMapping = new Mapping();

        Map<String, Map<String, String>> oMap = oMapping.classifyMapEntries();

        for ( String sParentKey : oMapping.coList )
        {
            Map<String, String> oChildMap = oMap.get(sParentKey);
            Iterator<String> oIterator = oChildMap.keySet().iterator();

            System.out.println("Map");
            while( oIterator.hasNext() )
            {
                String sChildKey = oIterator.next();
                System.out.print( "Key: " + sChildKey + ", Value: " 
                                    + oChildMap.get(sChildKey) + "\n");
            }
        }
    }

    private void init()
    {
        coMap = new HashMap<String, String>();
        coList = new ArrayList<String>();

        coMap.put("1_1", "a");
        coMap.put("1_19", "a");
        coMap.put("10_1", "b");
        coMap.put("10_19", "b");
    }

    private Map<String, Map<String, String>> classifyMapEntries()
    {
        Map<String, Map<String, String>> oClassified = 
            new HashMap<String, Map<String,String>>();

        Iterator<String> oIterator = coMap.keySet().iterator();
        while( oIterator.hasNext() )
        {
            String sKey = oIterator.next();

            String sFirst = sKey.substring(0,sKey.indexOf("_"));
            if ( !coList.contains(sFirst) )
            {
                coList.add(sFirst);
            }
        }

        for ( String sKey : coList )
        {
            Map<String, String> oChildMap = new HashMap<String, String>();

            Iterator<String> oIterator2 = coMap.keySet().iterator();
            while( oIterator2.hasNext() )
            {
                String sChildKey = oIterator2.next();
                String sParentKey = sChildKey.substring(0,sChildKey.indexOf("_"));

                if ( sKey.equals(sParentKey) )
                {
                    oChildMap.put(sChildKey, coMap.get(sChildKey));
                }
            }

            oClassified.put(sKey, oChildMap);
        }

        return oClassified;
    }

}