Java暑期学习第十六天日报

一、今天学习的新内容：

    今天练习5.8的的习题。

二、遇到的问题：

    无。

三、明天计划：

    明天开始学习6.1和6.2的内容。

 

具体内容如下：

 1.请分别定义父类people和子类Student，观察子类是如何共享父类属性和方法的。

public class People1 {
public int age;
public String name;
public String sex;
public People1() {
System.out.println("父类无参构造方法！");
}

public void say() {
System.out.println("父类方法say()");
}
public String getName() {
return this.name;
}
public static void main(String[] args) {

People1 s=new student(12,"小明","man",100021);
s.say();
String str=s.getName();
System.out.println("父类属性name:"+str);
}

}
class student extends People1{

private int idNumber;
public student() {

}
public student(int a,String n,String s,int id) {
age=a;
name=n;
sex=s;
idNumber=id;
System.out.println("子类含参构造方法！");

}
public student(int i) {
idNumber=i;
System.out.println("子类含参构造方法！");
}

}

测试截图：

 

 

2.在题1People中定义final方法，然后在类student 类中定义与该final相同的方法，观察student的变化

在父类中的final方法不能在子类student中重写。

 

 

public class People1 {
    public int age;
    public String name;
    public String sex;
    public People1() {
        System.out.println("父类无参构造方法！");
    }
    
    public void say() {
        System.out.println("父类方法say()");
    }
    public String getName() {
        return this.name;
    }
    public final void sayMe() {
        System.out.println("父类final方法sayMe()！");
    }
    public static void main(String[] args) {
        
        People1 s=new student(12,"小明","man",100021);
        s.say();
        String str=s.getName();
        System.out.println("父类属性name:"+str);
    }

}
class student extends People1{

    private int idNumber;
    public student() {
        
    }
    public void sayMe() {
        //不能覆盖父类中的final方法，编译器报错
        System.out.println("父类final方法sayMe()！");
    }
    public student(int a,String n,String s,int id) {
        age=a;
        name=n;
        sex=s;
        idNumber=id;
        System.out.println("子类含参构造方法！");
        
    }
    public student(int i) {
        idNumber=i;
        System.out.println("子类含参构造方法！");
    }
    
}

 

3.将题目1中的people类定义为抽象类，并由student来继承

public abstract class  People1 {
    public int age;
    public String name;
    public String sex;
    public People1() {
        System.out.println("父类无参构造方法！");
    }
    
    public  abstract void say();
    public abstract void get() ;
    
    public static void main(String[] args) {
        
        People1 s=new student(16,"小丽","woman",12211);
        s.say();
        s.get();
        
    }

}
class student extends People1{

    private int idNumber;
    public student() {
        
    }
    public void say() {
        System.out.println("父类方法say()");
    }
    public void get() {
        System.out.println("父类属性姓名："+name);
        System.out.println("父类属性年龄："+age);
        System.out.println("父类属性性别："+sex);
        System.out.println("子类属性学号："+idNumber);
    }
    public student(int a,String n,String s,int id) {
        age=a;
        name=n;
        sex=s;
        idNumber=id;
        System.out.println("子类含参构造方法！");
        
    }
    
    
}

测试截图：