Java 第14章 ：综合案例：继承分析

课时67：案例分析一（学生类）

补习一下this调用构造函数的例子：

public CrawlDatum(){} 
public CrawlDatum(int status, int fetchInterval) { 
    this(); /*this调用的作用是调用上面的无参构造函数*/ 
    this.status = (byte)status; 
    this.fetchInterval = fetchInterval; 
    } 
public CrawlDatum(int status, int fetchInterval, float score) { 
    this(status, fetchInterval); /*this的作用是调用上面有两个参数的构造函数*/
    this.score = score; 
    } 

1， 实现代码复用。例如上面第三个构造函数如果不使用this就会是这样

public CrawlDatum(int status, int fetchInterval, float score) { 
    this.status = (byte)status; 
    this.fetchInterval = fetchInterval; 
    this.score = score; 
  } 

这样的话，前两行代码就完全是第二个构造函数中的语句，违背面向对象代码复用的原则。

2， 封装 如果说第二个构造函数的实现发生了变化，则我们除了修改第二个构造函数，还得修改第三个构造函数。 如果使用this就不需要修改第三个构造函数了。

 

package test;
 class Person {
    private String name;
    private String addr;
    private char sex;
    private int age;
    public Person(){}
    public Person(String name,String addr){
        this(name,addr,'男',0);
    }
    public Person (String name,String addr,char sex,int age){
        this.name = name;
        this.addr = addr;
        this.sex = sex;
        this.age = age;
    }
    public String getInfo(){
        return "姓名："+ this.name + "、性别：" + this.sex+ "、年龄："+ this.age +"、地址："+ this.addr;
    }
}
class Student extends Person{
    private double match;
    private double english;
    public Student(){}  //无参
    public Student(String name , String addr){   //两参
        super(name,addr);
    }
    public Student(String name,String addr,char sex,int age,double match,double english){   //六参
        super(name,addr,sex,age);//重点!!! super应在首行调用
        this.match = match;
        this.english = english;
    }
    public String getInfo(){
        return super.getInfo() + "、数学成绩："+ this.match + "、英语成绩" + this.english ;
    }
}
public class example {
    public static void main(String[] args) {
        Student stu = new Student("暖光","天府广场",'男',3,99.8,99.9) ;
        System.out.println(stu.getInfo() );
        }
      }
/*
不能被继承的：
        　 1.私有的属性(可以通过set get或super方法使用父类的私有属性)
        　　2.不同包的friendly
        　　3.构造方法不能继承
 */

课时68：案例分析二（管理人员与职员）

package test;
class Employee{
    private String name;
    private int age;
    private String sex;
    public Employee(){}
    public Employee (String name,int age, String sex){
        this.name = name;
        this.age = age;
        this.sex = sex;
    }
    public String getInfo(){
        return "姓名："+this.name+"、年龄："+this.age+"、性别："+this.sex;
    }
}
class Manager extends Employee{
    private String job;
    private double yearSalary;
    public Manager (){}
    public Manager (String name,int age,String sex,String job,double yearSalary){   //继承父类此处也应该添加成员属性才可继承
        super(name,age,sex);
        this.job = job;
        this.yearSalary = yearSalary;
    }
    public String getInfo(){
        return "【管理层】："+super.getInfo() + "、职务："+this.job + "、年薪："+this.yearSalary ;
    }
}
class Worker extends Employee{
    private String department;
    private double monthSalary;
    public Worker(){}
    public Worker(String name,int age, String sex,String department,double monthSalary ){
        super(name,age,sex);
        this.department = department ;
        this.monthSalary = monthSalary ;
    }
    public String getInfo(){
        return "【职员】："+super.getInfo() +"、部门："+this.department +"、月薪："+this.monthSalary ;
    }
}
public class example {
    public static void main(String[] args) {
         Manager man = new Manager("张三",30,"男","主管",15000.00);
         Worker str = new Worker("李斯",25,"女","出纳",3000.00);
         System.out.println(man.getInfo());
         System.out.println(str.getInfo());
    }
      }

课时69：案例分析三（字符串统计）

统计“want you to know one thing”字母“n”、“o”出现次数。

方案1：心比一个单独的处理类

 

 

本文地址：https://blog.csdn.net/u012820292/article/details/109561011