列表
根据对象某个
字段进行
分组，在不同的编程语言中有不同的实现方法，以下是几种常见语言的示例：
###
Java
可以使用
Java 8 的 Stream API 实现。以`
List<SkyCashRate>`
根据`seclineName`
字段分组为例：
```
java
import
java.util.*;
import
java.util.stream.Collectors;
import org.apache.commons.lang3.StringUtils;
class SkyCashRate {
private String seclineName;
public SkyCashRate(String seclineName) {
this.seclineName = seclineName;
}
public String getSeclineName() {
return seclineName;
}
}
public class GroupByExample {
public static void main(String[] args) {
List<SkyCashRate>
list = new Array
List<>();
list.add(new SkyCashRate("A"));
list.add(new SkyCashRate("B"));
list.add(new SkyCashRate(null));
Map<String,
List<SkyCashRate>> seclineMap =
list.stream()
.collect(Collectors.groupingBy(m
-> StringUtils.isEmpty(m.getSeclineName()) ? "其他" : m.getSeclineName(), Collectors.to
List()));
System.out.println(seclineMap);
}
}
```
若要
分组后对
相关字段进行
计算，以`
List<Activity>`为例：
```
java
import
java.util.*;
import
java.util.function.Function;
import
java.util.stream.Collectors;
import
java.util.stream.Stream;
class Activity {
private int pv;
private int prizeCount;
public Activity() {
}
public Activity(int pv, int prizeCount) {
this.pv = pv;
this.prizeCount = prizeCount;
}
public int getPv() {
return pv;
}
public void setPv(int pv) {
this.pv = pv;
}
public int getPrizeCount() {
return prizeCount;
}
public void setPrizeCount(int prizeCount) {
this.prizeCount = prizeCount;
}
}
public class GroupAndCalculate {
private static
List<Activity> groupMergeTo
List(
List<Activity> data
List, Function<Activity, ?> groupFunc) {
return data
List.stream()
.collect(Collectors.groupingBy(groupFunc))
.values()
.stream()
.flatMap(
list -> Stream.of(
list.stream()
.reduce((data1, data2)
-> {
data1.setPv(data1.getPv() + data2.getPv());
data1.setPrizeCount(data1.getPrizeCount() + data2.getPrizeCount());
return data1;
})
.orElse(new Activity())))
.collect(Collectors.to
List());
}
public static void main(String[] args) {
List<Activity> activities = Arrays.as
List(
new Activity(10, 2),
new Activity(20, 3),
new Activity(10, 2)
);
List<Activity> result = groupMergeTo
List(activities, activity
-> activity.getPv());
System.out.println(result);
}
}
```
###
JavaScript
可以使用`for`循环实现
对象数组基于某个
字段分组，以
根据`gender`
字段分组为例：
```
javascript
const obj = [
{ name: '谢广坤', gender: 'male' },
{ name: '赵四', gender: 'male' },
{ name: '刘能', gender: 'male' },
{ name: '王小蒙', gender: 'female' }
];
type stringKey = Record<string, any[]>;
const result: stringKey = {};
const apartGroup = () => {
for (let i = 0; i < obj.length; i++) {
const key = obj[i].gender;
if (result[key]) {
result[key].push(obj[i]);
} else {
result[key] = [obj[i]];
}
}
console.log('result', result);
return result;
};
apartGroup();
```
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