Java对Map集合处理使用Stream流方式

作者: 楼兰King | 来源:发表于2024-01-02 16:45 被阅读0次

java stream操作，Collectors.groupBy
2020-07-20Stream流
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对一组String字符串，使用谷歌的Gson转换为Map<String, List<IndicatorPageDaoBO>，在对数据进行分组统计数量操作。

实体类:

public class IndicatorPageDaoBO {
    private Long indicatorIdentifierId;
    private Long indicatorValueId;
    private String periodId;
    private String institutionCode;
    private String productCode;
    private String nodeCode;
    private BigDecimal value;
    private BigDecimal amount;
}

主方法:

import cn.hutool.json.JSONUtil;
import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;
import com.IndicatorPageDaoBO;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
public class aaaaaa {
    public static void main(String[] args) {
        String zhi="{\"125629597553664-SDXZRB0005\":[{\"periodId\":\"8ac275c57fb20c99017fd49c994c0050\",\"amount\":null,\"productCode\":\"SDXZRB0005\"," +
                "\"institutionCode\":\"125629597553664\",\"nodeCode\":\"ZBDECJ002\",\"indicatorIdentifierId\":165761,\"indicatorValueId\":91929,\"value\":0}]," +
                "\"178040247342840-SDXZRB0002\":[{\"periodId\":\"8ac275c57fb20c99017fd49c994c0050\",\"amount\":null,\"productCode\":\"SDXZRB0002\"," +
                "\"institutionCode\":\"178040247342840\",\"nodeCode\":\"BJ001test\",\"indicatorIdentifierId\":165573,\"indicatorValueId\":90923,\"value\":0}]," +
                "\"B00002-SDXZRB0005\":[{\"periodId\":\"8ac275c57fb20c99017fd49c994c0050\",\"amount\":null,\"productCode\":\"SDXZRB0005\"," +
                "\"institutionCode\":\"B00002\",\"nodeCode\":\"1234561\",\"indicatorIdentifierId\":165571,\"indicatorValueId\":90921,\"value\":0}]," +
                "\"178040247342840-SDXZRB0001\":[{\"periodId\":\"8ac275c57fb20c99017fd49c994c0050\",\"amount\":null,\"productCode\":\"SDXZRB0001\"," +
                "\"institutionCode\":\"178040247342840\",\"nodeCode\":\"SHZJ001\",\"indicatorIdentifierId\":165575,\"indicatorValueId\":89421,\"value\":0}]," +
                "\"ZJTY001-SDXZRB0005\":[{\"periodId\":\"8ac275c57fb20c99017fd49c994c0050\",\"amount\":null,\"productCode\":\"SDXZRB0005\"," +
                "\"institutionCode\":\"ZJTY001\",\"nodeCode\":\"ZBDECJ002\",\"indicatorIdentifierId\":165557,\"indicatorValueId\":89423,\"value\":0}]," +
                "\"ZZGC001-SDXZRB0005\":[{\"periodId\":\"8ac275c57fb20c99017fd49c994c0050\",\"amount\":null,\"productCode\":\"SDXZRB0005\"," +
                "\"institutionCode\":\"ZZGC001\",\"nodeCode\":\"SHZJ001\",\"indicatorIdentifierId\":165521,\"indicatorValueId\":89425,\"value\":0}," +
                "{\"periodId\":\"8ac275c57fb20c99017fd49c994c0050\",\"amount\":null,\"productCode\":\"SDXZRB0005\",\"institutionCode\":\"ZZGC001\"," +
                "\"nodeCode\":\"ZBDECJ002\",\"indicatorIdentifierId\":165579,\"indicatorValueId\":90925,\"value\":0}]}";
        Gson gson = new Gson();
        Map<String, List<IndicatorPageDaoBO>> allMap = gson.fromJson(zhi, new TypeToken<Map<String, List<IndicatorPageDaoBO>>>() {}.getType());
        System.out.println(JSONUtil.toJsonStr(allMap));
        Map<String, Long> zhiMap = allMap.entrySet().stream()
                .flatMap(entry -> entry.getValue().stream())
                .collect(Collectors.groupingBy(
                        IndicatorPageDaoBO::getInstitutionCode,
                        Collectors.mapping(
                                IndicatorPageDaoBO::getProductCode,
                                Collectors.counting()
                        )
                ));
        System.out.println("按机构分组统计每个机构下产品总数量，机构为key,总量为value"+JSONUtil.toJsonStr(zhiMap));
/**
Map<String, List<IndicatorPageDaoBO>> mapList
现在有一个map集合数据indicatorPageDaoBOS，map中value值List<IndicatorPageDaoBO>，IndicatorPageDaoBO对象中有属性institutionCode，productCode，nodeCode。最终实现结果如下:
解析mapList,解析其中的value值List<IndicatorPageDaoBO>，根据institutionCode，productCode两个属性分组统计数量，最终返回
Map<String,Long> zhiMap集合的结果,zhiMap中key为institutionCode+","+productCode这两个属性值的拼接，value是分组后统计的数量
*/
        Map<String, Long> map = allMap.entrySet().stream()
                .flatMap(entry -> entry.getValue().stream())
                .collect(Collectors.groupingBy(
                        indicator -> String.format("%s,%s", indicator.getInstitutionCode(), indicator.getProductCode()),
                        Collectors.counting()
                ));
        System.out.println("按机构和产品分组，逗号分隔机构和品作为key，value为统计总量"+JSONUtil.toJsonStr(map));

    }
}