3大特点的
. 这节主要做下继承笔记.1. 继承
概念及使用在Java中,通过继承可以简化类
定义,扩展类功能. Java中支持类单继承和多层继承,但是不支持多继承,即: 个类只能继承个类而不能继承多个类.实现继承
格式为: 
子类名 extends 父类Java中继承只能直接继承父类中
公有属性和公有思路方法,而隐含地(不可见地)继承了私有属性. 继承内容如下图:
2. 子类对象
例子化过程子类对象在例子化时,需要注意
是: 子类对象例子化会默认先
父类中无参构造
,然后再子类构造思路方法. 例如下面例子代码: view plaincopy to clipboardpr
?Person
="">{
="alt">="keyword">privateStringname;
="">="keyword">private="keyword">age;
="alt">
="">="comment">//父类无参构造思路方法
="alt">="keyword">publicPerson
="">{
="alt">
.out.prln(="
">"
父类中构造思路方法");
="">}
="alt">="comment">//getter和
ter思路方法
="">="keyword">publicStringgetName
="alt">{
="">="keyword">
="keyword">this.name;
="alt">}
="">="keyword">public="keyword">voidName(Stringname)
="alt">{
="">="keyword">this.name=name;
="alt">}
="">="keyword">public="keyword">getAge
="alt">{
="">="keyword">="keyword">this.age;
="alt">}
="">="keyword">public="keyword">voidAge(="keyword">age)
="alt">{
="">="keyword">this.age=age;
="alt">}
="">="comment">//返回信息思路方法
="alt">="keyword">publicStringgetInfo
="">{
="alt">="keyword">="">"姓名是:"+name+="">",年龄是:"
+age;
="">}
="alt">}
="">="keyword">Student="keyword">extendsPerson
="alt">{
="">="keyword">privateStringschool=="">"软件Software学院";
="alt">="comment">//子类无参构造思路方法
="">="keyword">publicStudent
="alt">{
="">Name(="">"
saon");
="alt">Age(="number">23);
="">.out.prln(="">"子类中构造思路方法");
="alt">}
="">="keyword">public="keyword">voidpr
="alt">{
="">.out.prln(getInfo+="">",学校是:"+school);
="alt">}
="">}
="alt">="keyword">public="keyword">Demo01
="">{
="alt">="keyword">public="keyword">
="keyword">void
(Stringargs
)
="">{
="alt">="comment">//使用子类对象
="">Students=="keyword">Student;
="alt">s.pr;
="">}
="alt">}
="java" style="DISPLAY: none" rows="15" cols="95" name="code">
Person
{
private String name;
private age;
//父类无参构造思路方法
public Person
{
.out.prln("父类中构造思路方法");
}
//getter和ter思路方法
public String getName
{
this.name;
}
public void Name(String name)
{
this.name = name;
}
public getAge
{
this.age;
}
public void Age( age)
{
this.age = age;
}
//返回信息思路方法
public String getInfo
{
"姓名是: "+name+",年龄是: "+age;
}
}
Student extends Person
{
private String school = "软件Software学院";
//子类无参构造思路方法
public Student
{
Name("saon");
Age(23);
.out.prln("子类中构造思路方法");
}
public void pr
{
.out.prln(getInfo+",学校是:"+school);
}
}
public Demo01
{
public void (String args)
{
// 使用子类对象
Student s = Student ;
s.pr;
}
}
3.super
思路方法和类思路方法复写机制3.1 super
思路方法在上面
例子中, 实际上在子类Student构造思路方法中隐含了个super思路方法. 该思路方法表示父类(即超类)构造思路方法. 需要注意是,我们也可以使用super(参数类型 参数名, 参数类型 参数名, ...)这样格式来父类重载后含参构造思路方法. 下面例子中用到了这种super思路方法.3.2 子类对父类思路方法
复写子类可以继承父类
思路方法,也可以复写父类思路方法. 但复写父类思路方法有个基本前提: 所复写思路方法不能有比父类思路方法更严格访问权限. (访问权限 public > default > private)
这里举
个
例子,在该例子中, 子类Student以super(name,age)形式父类构造思路方法,同时子类以不变权限复写了父类getInfo思路方法: view plaincopy to clipboardpr
?Person
="">{
="alt">="keyword">privateStringname;
="">="keyword">private="keyword">age;
="alt">="comment">//希望在Person类构造思路方法时候可以直接为属性
化
="">="keyword">publicPerson(Stringname,="keyword">age)
="alt">{
="">="keyword">this.Name(name);
="alt">="keyword">this.Age(age);
="">}
="alt">="comment">//私有属性要加入ter和getter操作就可以访问了
="">="keyword">public="keyword">voidName(Stringname)
="alt">{
="">="keyword">this.name=name;
="alt">}
="">="keyword">public="keyword">voidAge(="keyword">age)
="alt">{
="">="keyword">this.age=age;
="alt">}
="">="keyword">publicStringgetName
="alt">{
="">="keyword">="keyword">this.name;
="alt">}
="">="keyword">public="keyword">getAge
="alt">{
="">="keyword">="keyword">this.age;
="alt">}
="">="keyword">publicStringgetInfo
="alt">{
="">="keyword">="">"姓名="+="keyword">this.name+="">"
年龄="+="keyword">this
.age;
="alt">}
="">}
="alt">="comment">//和Person类相比是扩充了Person类功能所以此处继承即可
="">="keyword">StudentextendsPerson
="alt">{
="">="keyword">privateStringschool;
="alt">
="">="keyword">publicStudent(Stringname,="keyword">age,Stringschool)
="alt">{
="">="comment">//super;//-->隐含代码
="alt">="comment">//此时最好可以明确指出要父类中有两个参数构造思路方法
="">="comment">//直接指明父类中有两个参数构造思路方法
="alt">super(name,age);
="">="keyword">this.School(school);
="alt">}
="">="keyword">public="keyword">voidSchool(Stringschool)
="alt">{
="">="keyword">this.school=school;
="alt">}
="">="keyword">publicStringgetSchool
="alt">{
="">="keyword">="keyword">this.school;
="alt">}
="">="comment">//子类覆写了父类中getInfo思路方法
="alt">="keyword">publicStringgetInfo
="">{
="alt">="comment">//父类中getInfo思路方法,使用super.思路方法名格式
="">="keyword">super.getInfo+="">"学校="+="keyword">this.school;
="alt">}
="">}
="alt">="keyword">public="keyword">Demo02{
="">="keyword">public="keyword">="keyword">void(Stringargs)
="alt">{
="">="comment">//使用子类对象
="alt">Students=="keyword">Student(="">"saon",23,="">"软件Software学院");
="">.
="keyword">out.prln(s.getInfo);
="alt">}
="">}
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