使用private私有化

 public static void main(String[] args) {
        person c1 = new person();
        c1.name = "王海燕";
        c1.setage(18);
        System.out.println(c1.getage());

    }
}

class person{
    String name;
    private int age;

    public void setage(int a){
        if(a > 0 && a < 150)
        age = a;
        else
            System.out.println("no");
    }

    public int getage(){
        return age;
    }
   /* public void speak(){
        System.out.println(name + "..." +age);
    }*/

}