使用Java将地图内容存储到另一个地图中

Question

I have the below java class

public class DataStruc {

    private List<String> TradeRef;
    private List<String> TMS;

     public DataStruc(List<String> TradeRef, List<String> TMS) {
        setTradeRef(TradeRef);
        setTMS(TMS);
    }

    //setters and getters for them

    }

I have the below map which is as shown below and into which i am explicitly creating the list

Map<String, DataStruc> newdatamap = new HashMap<String, DataStruc>();
List<String> B1TradeRef = Arrays.asList("TradRefr", "tr1");
List<String> B1TMS = Arrays.asList("TS", "TMSW");

List<String> B2TradeRef = Arrays.asList("TradRefrtsy", "tr1ty");
List<String> B2TMS = Arrays.asList("TWES", "TUYTMSW");

newdatamap.put("B1", new DataStruc (B1TradeRef,B1TMS));
newdatamap.put("B2", new DataStruc (B2TradeRef,B2TMS));

below is the output of the above program as shown below

output :-
*******

B1 = com.asd.ert.DataStruc@1394894
B2 = com.asd.ert.DataStruc@1394894

Now I want to retrieve the value of above HashMap named newdatamap as I want to store it like this format in another map named finalmap .Please advise how to achieve this?

lets say my finalmap declartion is like

Map<String , String> finalmap = new HashMap<String , String>();

so if newdatamap.keyset is equal to B1 then following should be stored in finalmap .Please advise how to achieve this

TradRefr                TradeRef
tr1                     TradeRef //class member name declartions
TS                       TMS 
TMSW                     TMS     //class member name declartions

Answer 1

Try this:

    Map<String , String> finalmap = newdatamap.values().stream()
        .flatMap(d -> Stream.concat(
            d.getTradeRef().stream().map(s -> new SimpleEntry<>(s, "TradeRef")),
            d.getTMS().stream().map(s -> new SimpleEntry<>(s, "TMS"))))
        .collect(Collectors.toMap(e -> e.getKey(), e -> e.getValue()));
    System.out.println(finalmap);
    // -> {TUYTMSW=TMS, tr1=TradeRef, TradRefrtsy=TradeRef, TWES=TMS, TradRefr=TradeRef, TMSW=TMS, TS=TMS, tr1ty=TradeRef}

class SimpleEntry is an public inner class of java.util.AbstractMap.

Answer 2

TMSW TMS // class member name declartions

So you want to extract field names here of class DataStruc . There is only one way to do that in java, which is using reflection API.

Your DataStruc class

import java.util.List;

    public class DataStruc {

        private List<String> TradeRef;
        private List<String> TMS;

        public DataStruc(List<String> TradeRef, List<String> TMS) {
            this.TradeRef = TradeRef;
            this.TMS = TMS;
        } // setters and getters for them

    }

Calling class.

import java.lang.reflect.Field;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class MainClass {
    public static void main(String[] args) throws IllegalArgumentException,
            IllegalAccessException {

        Map<String, DataStruc> newdatamap = new HashMap<String, DataStruc>();
        List<String> B1TradeRef = Arrays.asList("TradRefr", "tr1");
        List<String> B1TMS = Arrays.asList("TS", "TMSW");

        List<String> B2TradeRef = Arrays.asList("TradRefrtsy", "tr1ty");
        List<String> B2TMS = Arrays.asList("TWES", "TUYTMSW");

        newdatamap.put("B1", new DataStruc(B1TradeRef, B1TMS));
        newdatamap.put("B2", new DataStruc(B2TradeRef, B2TMS));

        Map<String, String> finalmap = new HashMap<String, String>();
        // loop through current map
        for (Map.Entry<String, DataStruc> entry : newdatamap.entrySet()) {

            String key = entry.getKey();
            DataStruc dataStruc = entry.getValue();

            // get all the fields of object dataStruc
            for (Field field : dataStruc.getClass().getDeclaredFields()) {
                field.setAccessible(true);
                String fieldName = field.getName();
                // check if field is List<String>
                if (field.get(dataStruc) instanceof List) {
                    List<String> fieldValue = (List<String>) field.get(dataStruc);
                    // if yes then add the List entries to your final map with
                    // current field name
                    for (String str : fieldValue) {
                        finalmap.put(str, fieldName);
                    }
                }

            }
        }

        for (Map.Entry<String, String> entry : finalmap.entrySet())
            System.out.println(entry.getKey() + "-" + entry.getValue());

    }

}

Output after running Main class

TUYTMSW-TMS
tr1-TradeRef
TradRefrtsy-TradeRef
TWES-TMS
TradRefr-TradeRef
TMSW-TMS
tr1ty-TradeRef
TS-TMS