One: Understanding of method rewriting
Note: distinguish between overloading and rewriting
Two: practice
Example 1
Person.java
package com.xx.study;
public class Person {
String name;
int age;
public Person() {
}
public Person(String name,int age) {
this.name=name;
this.age=age;
}
public void eat() {
System.out.println("吃饭");
}
public void sleep(int time) {
System.out.println("睡觉"+time+"小时");
show();
}
private void show() {
System.out.println("今天要早睡啊");
}
public Object info() {
return null;
}
}
Student.java
package com.xx.study;
public class Student extends Person {
String major;
public Student() {
}
public Student(String major) {
this.major = major;
}
public void study() {
System.out.println("专业是" + major);
}
// 对父类的eat方法重写
public void eat() {
System.out.println("吃减脂餐");
}
// 特殊情况，子类中不能重写父类中声明为private权限的方法，显示的还是父类的值
public void show() {
System.out.println("dd");
}
/*
* 父类Object的重写 父类重写的方法的返回值类型是A类型，
* 则子类重写的方法类型可以是A类或A的子类
* String是Object的子类
*/
public String info() {
return null;
}
}
PersonTest.java
package com.xx.study;
public class PersonTest {
public static void main(String[] args) {
Student s=new Student("计算机科学与技术");
s.eat();
s.sleep(10);
s.study();
}
}
Example 2
Private cannot overwrite
Kids.java
package com.xzx.contact;
public class Kids extends ManKind{
private int yearsOld;
public Kids() {
}
public Kids(int yearsOld) {
this.yearsOld=yearsOld;
}
public int getyearsOld() {
return yearsOld;
}
public void setyearsOld(int yearsOld) {
this.yearsOld=yearsOld;
}
public void printAge() {
System.out.println(yearsOld);
}
public void employeed() {
System.out.println("Kids should study and no job");
}
}
KidsTest.java
package com.xzx.contact;
public class KidsTest {
public static void main(String[] args) {
Kids someKids = new Kids();
someKids.setSalary(100000);
System.out.println(someKids.getSalary());
Kids someKids2 = new Kids(1);
System.out.println(someKids2.getyearsOld());
someKids.employeed();
}
}
Three: the difference between rewriting and reloading
