Java面向对象基础详解

public class Phone {
    public int price=3999;
    public String brand="华为";
    public static void playGame(){
        System.out.println("这手机可以打游戏");
    }
}

public class PhoneDemo {
    public static void main(String[] args) {
        Phone p=new Phone();//创建对象
        System.out.println(p.brand);
        System.out.println(p.price);
        p.playGame();
    }
}

 
 
    public class Student {
        private String name;
        private int age;
        public Student(){}//无参构造
       public Student(String name,int age){// 有参构造
           if(age<0){
               System.out.println("你输入的年龄有误，默认为18岁");
               this.age=18;   this.name=name;}
           else{
           this.age=age;this.name=name;}
       }
       public void setName(String name){//get/set方法
           this.name=name;
       }
       public String getName(){
            return name;
        }
       public void setAge(int age){
           if(age<0){
               System.out.println("你输入的年龄有误，默认为18岁");
               this.age=18;
           }else{
               this.age=age;
           }
       }
       public int getAge(){
           return age;
       }
}

public class StudentDemo {
    public static void main(String[] args) {
        Student s=new Student();//创建无参对象
        s.setAge(20);
        s.setName("张三");
        System.out.println(s.getName()+" ,"+s.getAge());
        s=new Student("李四",-1);//创建对象的同时赋值
        System.out.println(s.getName()+","+s.getAge());
    }
}