字段私有化 + getter/setter 的完整写法。
private int age; 与 private String name; 字段私有化public Puppy(String name){ this.name = name; }setAge(int age)、getAge()、getName() 提供访问入口Puppy p = new Puppy("Tommy");p.setAge(2); → 2p.getName(); → Tommythis.name = name; —— this 指向当前对象