Merging data based on ids in different objects in Java in a efficient way-CodePudding

I have few objects in a sheet object identified by ids , i want to merge these 3 objects by ids keeping in mind that all ids from all object should be there in the final sheet.

Although i can get all ids form object 1 serach in other object and add it , but i think there must be some smarter way of doing it .

Data @Data @NoArgsConstructor @AllArgsConstructor @Builder public class Data { int id ; int amount1 ; int amount2 ; int amount3 ;

            }
            
            Data data1 = new Data(7001,20,20,10);
            Data data2 = new Data(8002,30,30,10);
            Data data3 = new Data(7003,30,40,10);
            
            List ls = new ArrayLisy();
            ls.add(data1);
            ls.add(data2);
            ls.add(data3);
            
            Map<String,List<Data>> localMap = new HashMap();
            localMap.put("sheet1",ls);

Similary we have sheet2 and sheet3 with same or some different ids as

            Data data1 = new Data(7001,5,0,2);
            Data data2 = new Data(8004,2,2,2);
            Data data3 = new Data(7003,3,4,5);
            
            List ls = new ArrayLisy();
            ls.add(data1);
            ls.add(data2);
            ls.add(data3);
            
            Map<String,List<Data>> localMap = new HashMap();
            localMap.put("sheet2",ls);

Now i just wand to Merge the Sheets to have one sheet with Sum of fields as

Final sheet data sheetFinal should have a list of Data like where id 7001 has amount1 added from all sheet (20 5) for amount1.

            Data data1 = new Data(7001,25,20,12) ;
            Data data2 = new Data(8002,30,30,10) ;
            Data data3 = new Data(8004,2,2,2) ;
            Data data4 = new Data(7003,33,44,20) ;

How can i merge the sheet by ids and get a final sheet with all data in a smarter and memory efficient way ? Thanks in

CodePudding user response：

Something like this? If its defined in the Data class we can lose the static and all the getters and setters.

public static List<Data> sum(Map<String, List<Data>> localMap) {
    Map<Integer,Data> indexedAccumulator = new HashMap<>(); // indexed on Data.id
    for(List<Data> localMapEntry: localMap.values()) {
        for(Data data : localMapEntry) {
            int id = data.getId();
            if(indexedAccumulator.containsKey(id)) {
                Data sumData = indexedAccumulator.get(id);
                sumData.setAmount1(sumData.getAmount1()   data.getAmount1());
                sumData.setAmount2(sumData.getAmount2()   data.getAmount2());
                sumData.setAmount3(sumData.getAmount3()   data.getAmount3());
                
            } else {
                indexedAccumulator.put(id, new Data(id, data.getAmount1(), data.getAmount2(), data.getAmount3())); // new object to preserve original
            }
        }
        
    }

    List<Data> sheetFinal = new ArrayList<>();
    for (Data summedData : indexedAccumulator.values()) {
        sheetFinal.add(summedData);
    }
    
    return sheetFinal;
}