class Average{
 private int[] fractions = new int[3]; //分数
 private int average = 0; //平均分
 public void setFraction(int[] fraction){
  fractions = fraction;
 }
 public double getAverage(){
  for(int cell:fractions){
   average += cell;
  }
  return (double) (average / fractions.length);
 }
}
class app{
 public static void main(String[] args){
  int[] a = {50,40,50};
  Average average = new Average();
  average.setFraction(a); //设置分数
  double n = average.getAverage(); //获取平均分
  System.out.println(average.average); //报错
  System.out.println(n); //46.0
 }
}

class Animal{
 private String name;
 private int age;

 public void setName(String name){
  this.name = name;
 }
 public void setAge(int age){
  this.age = age;
 }
 public String getName(){
  return this.name;
 }
 public int getAge(){
  return this.age;
 }
}
class Cat extends Animal{
 public void voice(){
  System.out.println(super.getName() + " 喵");
 }
 public void eat(){
  System.out.println(super.getName() + " fish");
 }
}
class Dog extends Animal{
 public void voice(){
  System.out.println(super.getName() + " 汪");
 }
 public void eat(){
  System.out.println(super.getName() + " Bone");
 }
}
class app{
 public static void main(String[] args){
  Cat cat = new Cat();
  cat.setName("猫大王"); //Cat本身没有setName方法，但是它的基类有，所以java解析器会到Cat的基类那里拿
  cat.voice();
  Dog dog = new Dog();
  dog.setName("大黑");
  dog.setAge(13);
  dog.voice();
  System.out.println(dog.getName() + dog.getAge());
 }
}

------Output------
猫大王 喵
大黑 汪
大黑13

class Animal{
 private String name;
 private int age;

 public void setName(String name){
  this.name = name;
 }
 public void setAge(int age){
  this.age = age;
 }
 public String getName(){
  return this.name;
 }
 public int getAge(){
  return this.age;
 }
}
class Dog extends Animal{
 public String getName(){
  return super.getName() + "2";
 }
 public void voice(){
  System.out.println(super.getName() + " 汪");
 }
 public void eat(){
  System.out.println(super.getName() + " Bone");
 }
}
class app{
 public static void main(String[] args){
  Dog dog = new Dog();
  dog.setName("大黑");
  System.out.println(dog.getName()); //执行的是Dog中的getName方法
 }
}

class Animal{
 private String name;
 public void setName(String name){
  this.name = name;
 }
 public String getName(){
  return this.name;
 }
}
class Dog extends Animal{
 public int getName(){ //和父类中的getName返回值不同，报错
  return 123;
 }
}
class app{
 public static void main(String[] args){
  Dog dog = new Dog();
  System.out.println(dog.getName());
 }
}

class Animal{
 private String name;

 public void setName(String name){
  this.name = name;
 }
 public String getName(String hello){
  return this.name + hello;
 }
}
class Dog extends Animal{
 public String getName(){
  return "123";
 }
}
class app{
 public static void main(String[] args){
  Dog dog = new Dog();
  dog.setName("大黑");
  System.out.println(dog.getName("hello"));
 }
}

------Output------
大黑hello

class Animal{
 public int age = 5;

 public int getAge(){
  return age;
 } 
}
class Dog extends Animal{
 public int age = 8;

 public int getAge(){
  return age + 2;
 }
}
class app{
 public static void main(String[] args){
  Animal dog = new Dog();
  System.out.println(dog.age);
 }
}

------Output------
5

class Animal{
 public int age = 5;
 public int getAge(){
  return age;
 }
}
class Dog extends Animal{
 public int age = 8;

 public int getAge(){
  return age + 2;
 }
 public setAge(int a){
  this.age = a;
 }
}
class app{
 public static void main(String[] args){
  Animal dog = new Dog();
  System.out.println(dog.setAge(5));
 }
}

class Animal{
 public int age = 5;

 public int getAge(){
  return age;
 }
}
class Dog extends Animal{
 public int getAge(){
  return age + 2;
 }
}
class Cat extends Animal{
 public int getAge(){
  return age + 3;
 }
}
class app{
 public static void main(String[] args){
  Animal dog = new Dog();
  Animal cat = new Cat();

  System.out.println(dog.getAge());
  System.out.println(cat.getAge());
 }
}

------Output------
7
8

class Animal{
 public int age = 5;

 public int getAge(){
  return age;
 }
}
class Dog extends Animal{
 public int getAge(){
  return age + 2;
 }
}
class Cat extends Animal{
 public int getAge(){
  return age + 3;
 }
}
class app{
 public static void main(String[] args){
  Animal[] animals = new Animal[2];
  animals[0] = new Dog();
  animals[1] = new Cat();

  System.out.println(animals[0].getAge());
  System.out.println(animals[1].getAge());
 }
}

------Output------
7
8