Java8 stream排序数值字符串类型降序或者升序，stream groupby分组统计属性值出现多少次和一共有多少属性值出现
Java8 stream排序数值字符串类型降序或者升序，如果不对字符串进行特殊处理，会出现 "77" 排在"111"这样的数值字符串前面的情况，实际77是比111要小，因此需要对字符串处理下。
元数据：
[
{
"poiCode": "101001",
"poiName": "歌剧厅",
"portraitKey": "福建",
"portraitTitle": "客源分布",
"portraitValue": "380.00",
"ratio": "9.91"
},
{
"poiCode": "101001",
"poiName": "歌剧厅",
"portraitKey": "江西",
"portraitTitle": "客源分布",
"portraitValue": "228.00",
"ratio": "5.94"
},
{
"poiCode": "101001",
"poiName": "歌剧厅",
"portraitKey": "甘肃",
"portraitTitle": "客源分布",
"portraitValue": "567.00",
"ratio": "14.78"
},
{
"poiCode": "101001",
"poiName": "歌剧厅",
"portraitKey": "广东",
"portraitTitle": "客源分布",
"portraitValue": "438.00",
"ratio": "11.42"
},
{
"poiCode": "101001",
"poiName": "歌剧厅",
"portraitKey": "吉林",
"portraitTitle": "客源分布",
"portraitValue": "277.00",
"ratio": "7.22"
},
{
"poiCode": "101001",
"poiName": "歌剧厅",
"portraitKey": "陕西",
"portraitTitle": "客源分布",
"portraitValue": "199.00",
"ratio": "5.19"
},
{
"poiCode": "20101001",
"poiName": "京香苑烤鸭",
"portraitKey": "山西",
"portraitTitle": "客源分布",
"portraitValue": "192.00",
"ratio": "5.01"
},
{
"poiCode": "20201003",
"poiName": "三福百货",
"portraitKey": "贵州",
"portraitTitle": "客源分布",
"portraitValue": "175.00",
"ratio": "4.56"
},
{
"poiCode": "101001",
"poiName": "歌剧厅",
"portraitKey": "江苏",
"portraitTitle": "客源分布",
"portraitValue": "148.00",
"ratio": "3.86"
},
{
"poiCode": "20201003",
"poiName": "三福百货",
"portraitKey": "湖北",
"portraitTitle": "客源分布",
"portraitValue": "147.00",
"ratio": "3.83"
}
]因此使用如下代码段进行排序
source.stream().sorted(Comparator.comparing(TouristPortraitODTO::getPortraitValue,Comparator.comparingDouble(Double::parseDouble)).reversed()).limit(10).collect(Collectors.toList());
comparing第一个参数是排序字段，第二个参数是将前面的字段转成数值类型，本示例是因为数值为double类型，如果你是int类型可以使用Integer::parseInt即可，然后看看转换后的效果如下：
[
{
"poiCode": "101001",
"poiName": "歌剧厅",
"portraitKey": "甘肃",
"portraitTitle": "客源分布",
"portraitValue": "567.00",
"ratio": "14.78"
},
{
"poiCode": "101001",
"poiName": "歌剧厅",
"portraitKey": "广东",
"portraitTitle": "客源分布",
"portraitValue": "438.00",
"ratio": "11.42"
},
{
"poiCode": "101001",
"poiName": "歌剧厅",
"portraitKey": "福建",
"portraitTitle": "客源分布",
"portraitValue": "380.00",
"ratio": "9.91"
},
{
"poiCode": "101001",
"poiName": "歌剧厅",
"portraitKey": "吉林",
"portraitTitle": "客源分布",
"portraitValue": "277.00",
"ratio": "7.22"
},
{
"poiCode": "101001",
"poiName": "歌剧厅",
"portraitKey": "江西",
"portraitTitle": "客源分布",
"portraitValue": "228.00",
"ratio": "5.94"
},
{
"poiCode": "101001",
"poiName": "歌剧厅",
"portraitKey": "陕西",
"portraitTitle": "客源分布",
"portraitValue": "199.00",
"ratio": "5.19"
},
{
"poiCode": "20101001",
"poiName": "京香苑烤鸭",
"portraitKey": "山西",
"portraitTitle": "客源分布",
"portraitValue": "192.00",
"ratio": "5.01"
},
{
"poiCode": "20201003",
"poiName": "三福百货",
"portraitKey": "贵州",
"portraitTitle": "客源分布",
"portraitValue": "175.00",
"ratio": "4.56"
},
{
"poiCode": "101001",
"poiName": "歌剧厅",
"portraitKey": "江苏",
"portraitTitle": "客源分布",
"portraitValue": "148.00",
"ratio": "3.86"
},
{
"poiCode": "20201003",
"poiName": "三福百货",
"portraitKey": "湖北",
"portraitTitle": "客源分布",
"portraitValue": "147.00",
"ratio": "3.83"
}
]jdk8的stream还支持groupby，对list的某个属性进行分组可以用于统计某个属性总共出现多少次，和一个有多少个属性值出现。用法如下：
if(!CollectionUtils.isEmpty(contingencyDeviceIDTOList)){
Map collectFileId = contingencyDeviceIDTOList.stream().collect(Collectors.groupingBy(doc -> doc.getCmdFileId(), Collectors.counting()));
if(Objects.nonNull(collectFileId) && collectFileId.entrySet().size()>1){
throw new RCException("同一批设备只能选一个音频!");
}
}