在Person类的基础上，添加一个静态变量avgAge表示所有平均年龄。

[java]代码库

import java.util.Scanner;
public class Main{
	public static void main(String[] args) {
         Scanner scan = new Scanner(System.in);
         String n1 = scan.next();
         String s1 = scan.next();
         int a1 = scan.nextInt();
         Person p1 = new Person(n1, s1, a1);
         String n2 = scan.next();
         String s2 = scan.next();
         int a2 = scan.nextInt();
         Person p2 = new Person(n2, s2, a2);
         String n3 = scan.next();
         String s3 = scan.next();
         int a3 = scan.nextInt();
         Person p3 = new Person(n3, s3, a3);
         int avg = p3.getAvgAge()/3;
         System.out.print(avg);
         scan.close(); 
    }
} 

class Person {
	private String name;
	private String sex;
	private int age;
	private static int avgAge = 0;
	public Person(String n, String s, int a) {
		name = n;
		sex = s;
		age = a;
		avgAge = avgAge + a;
	}
	public int getAvgAge(){
		return avgAge;
	}
}
用数组：
import java.util.*; 
public class Main{
	
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int i;
		Person [] p = new Person[3];
		for(i = 0; i < 3; i++) {
			String name = scan.next();
			String sex = scan.next();
			int age = scan.nextInt();
			p[i] = new Person(name, sex, age);
		}
        System.out.println(p[2].getAvgAge()/3);
		scan.close();
	}
}

class Person{
    String name;
    String sex;
    int age;
    static int avgAge = 0;
    public Person(String n, String s, int a) {
    	name = n;
    	sex = s;
    	age = a;
    	avgAge += age;
    }
    public int getAvgAge() {
    	return avgAge;
    }
}