[JAVA] Find the average age from List <Person>.

Table of Contents ⇒ Java Algorithm Library-Artery-Sample

Q01_07.java

package jp.avaj.lib.algo;

import java.util.ArrayList;
import java.util.List;

import jp.avaj.lib.test.L;

/**
 *  List<Person>Find the average age from.
 *
 *・ Target data from Person(age)You need to define ArCreator to retrieve.
 *-In the first method, the convert method is implemented to extract the age..
 *-However, this method is troublesome because an implementation is created for each field to be extracted..
 *-In the second method, a general-purpose ArCreatorByName is created and the field name is specified..
 *・ It is possible to prevent the number of ArCreator implementations from increasing unnecessarily..
 *
 */
public class Q01_07 {
  public static void main(String[] args) throws Exception {
    List<Person> list = createList();

    //Definition of ArCreator-First way
    ArCreator<Person,Integer> creator = new ArCreator<Person,Integer>() {
      @Override
      public Integer convert(Person obj) throws Exception {
        return obj.getAge();
      }
    };
    //Find the average value
    L.p(ArList.avg(list,creator)+"");

    //Definition of ArCreator-Second method
    creator = new ArCreatorByName<Person,Integer>("age");
    //Find the average value
    L.p(ArList.avg(list,creator)+"");
  }

  /**Create personal information*/
  private static List<Person> createList() {
    List<Person> list = new ArrayList<Person>();
    list.add(new Person("a",25));
    list.add(new Person("b",30));
    list.add(new Person("c",28));
    list.add(new Person("d",22));
    list.add(new Person("e",38));
    return list;
  }

  /**Person information class(Only name and age..) */
  static class Person {
    public Person(String name,int age) {
      this.name = name;
      this.age = age;
    }
    private String name;
    private int age;
    public String getName() {
      return name;
    }
    public void setName(String name) {
      this.name = name;
    }
    public int getAge() {
      return age;
    }
    public void setAge(int age) {
      this.age = age;
    }
  }
}

The result is as follows.

result.txt

28.6
28.6