1 class Person {
 2   String name;
 3   private int age;
 4   public boolean setAge(int newAge) {
 5     if(newAge>=5&&newAge<=20) {
 6       age=newAge;
 7       return true;
 8     }
 9     else { 
10       return false;
11     }
12   }
13   public int getAge() {
14     return age;      
15   }
16 }

 1 import java.util.*;
 2 public class App1 {
 3   public static void main(String[] args) {
 4     Person s1=new Person();
 5     s1.name="张三";
 6     int a;
 7     System.out.print("请输入年龄:");
 8     Scanner reader=new Scanner(System.in);
 9     a=reader.nextInt();
10     if(s1.setAge(a)==true) {
11       System.out.println(s1.name+"年龄为:"+a);
12     }
13     else
14       System.out.println("输入错误");
15   }
16 }