java8 lambda Stream 将分組後的對象所有字段相加得到一個對象

• 資料結構

  現有多個對象，存儲每個租戶的視訊/音頻/圖檔大小，對象結構如下

public class TBucketSize  {
    private Long tenantId;
    private Long imgSize;
    private Long audioSize;
    private Long videoSize;
}
           

   租戶資料如下：

TBucketSize tBucketSize1=new TBucketSize();
        tBucketSize1.setTenantId(1L);
        tBucketSize1.setAudioSize(1L);
        tBucketSize1.setVideoSize(0L);
        tBucketSize1.setImgSize(0L);

        TBucketSize tBucketSize2=new TBucketSize();
        tBucketSize2.setTenantId(1L);
        tBucketSize2.setVideoSize(1L);
        tBucketSize2.setAudioSize(1L);
        tBucketSize2.setImgSize(2L);

        TBucketSize tBucketSize3=new TBucketSize();
        tBucketSize3.setTenantId(2L);
        tBucketSize3.setImgSize(1L);
        tBucketSize3.setAudioSize(0L);
        tBucketSize3.setVideoSize(0L);

        TBucketSize tBucketSize4=new TBucketSize();
        tBucketSize4.setTenantId(2L);
        tBucketSize4.setImgSize(1L);
        tBucketSize4.setAudioSize(3L);
        tBucketSize4.setVideoSize(1L);
        List<TBucketSize> bucketSizes=        Arrays.asList(tBucketSize1,tBucketSize2,tBucketSize3,tBucketSize4);
           

• 需求

         要求統計每個租戶 視訊/音頻/圖檔用量

•  java  stream lambda計算寫法：

bucketSizes.stream().collect(Collectors.toMap(TBucketSize::getTenantId, Function.identity(), (u1, u2) -> {
            u1.setImgSize(u1.getImgSize() + u2.getImgSize());
            u1.setVideoSize(u1.getVideoSize() + u2.getVideoSize());
            u1.setAudioSize(u1.getAudioSize() + u2.getAudioSize());
            return u1;
        })).forEach((k, v) -> System.out.println(k+"-->"+ JSON.toJSON(v)));
           

• 輸出結果

1-->{"audioSize":2,"imgSize":2,"isDelete":0,"videoSize":1,"tenantId":1}
2-->{"audioSize":3,"imgSize":2,"isDelete":0,"videoSize":1,"tenantId":2}