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Editor to share with you how to use Java Stream API to convert List into Map according to custom grouping rules. I believe most people don't know much about it, so share this article for your reference. I hope you can learn a lot after reading this article. Let's learn about it together.

The test data are four employee object instances in List:

Group according to the city where the employees are located:

The results were divided into three groups:

The employees of the first group are in Shanghai:

The employees of the second group are in Chengdu:

Count the number of employees in each group:

Divide employees into groups. Those with a score greater than 101 are in one group, and those less than or equal to 101 are in another group:

Grouping result:

Package java8;import java.util.ArrayList;import java.util.List;import java.util.Map;import java.util.Map.Entry;import java.util.function.Consumer;import java.util.stream.Collectors;class Employee {private String city; private String name; private int score; public Employee (String name, String city, int score) {this.city = city; this.name = name; this.score = score } public String getCity () {System.out.println ("city:" + this.city); return this.city;} public String getName () {return this.name;} public int getScore () {return this.score;} @ Override public String toString () {return String.format ("Employee:" + this.name + "city:" + this.city) }} class Person {private String name; private int age; Person (String name, int age) {this.name = name; this.age = age;} @ Override public String toString () {return String.format ("Person {name='%s', age=%d}", name, age);} / / Jerry 2016-01-15 20:51PM? Type, which is mostly used for extends generic, accepts all Object's sub classpublic class StreamTest {private static void printMap (Map)

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