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1、 Person、Student类定义在JavaOop类里面，属于内部类， private String school是private 级别，Student类的s实例可以直接引用 School属性

2、将Person、Student类定义在JavaOop类外面，属于外部类，private String school是private 级别，Student类不可以直接引用 School属性，必须s.getSchool()来调用

package IMF;

public class JavaOop {

public static void main(String[] args) {

// TODO Auto-generated method stub

Student s = new Student();

s.setName("Spark");

s.setAge(6);

s.setSchool("Big Data");

System.out.println("Name:"+ s.getName() +" age" + s.getAge()+" school "+ s.getSchool());

s.sayHello();

Cat cat = new Cat();

cat.act();

Dream bigData = new BigData();

bigData.toDo();

}

}

class BigData implements Dream{

@Override

public void toDo() {

// TODO Auto-generated method stub

System.out.println("Life is short ,you need spark!");

}

}

interface Dream{

public String ID ="001";

public void toDo();

}

abstract class Animal{

private String name;

public abstract void act();

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

}

class Cat extends Animal{

@Override

public void act() {

// TODO Auto-generated method stub

System.out.println("cat doing");

}

}

class Person {

private String name;

private int age;

final void sayHello(){

System.out.println("Person say HEllo");

}

public Person () {

System.out.println("Person's constructor!");

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public int getAge() {

return age;

}

public void setAge(int age) {

this.age = age;

}

}

class Student extends Person {

private String school;

/*void sayHello(){

super.sayHello();

System.out.println("Student say HEllo");

}*/

public String getSchool() {

return school;

}

public void setSchool(String school) {

this.school = school;

}

public Student () {

System.out.println("Student constructor!");

}

}

运行结果如下：

Person's constructor!

Student constructor!

Name:Spark age6 school Big Data

Person say HEllo

cat doing

Life is short ,you need spark!

因为水平有限，难免有疏忽或者不准确的地方，希望大家能够直接指出来，我会及时改正。一切为了知识的分享。

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