Java面向对象之继承性的实例代码详解

public class Animal {
 int age;
 String name;
 public void eat(){
  System.out.println("动物可以吃东西");
 }
}

public class Dog extends Animal{
 public void eat(){
  System.out.println(age+"岁的狗狗可以吃东西");
 }
 public static void main(String[] args) {
  Dog dog1 = new Dog();
  dog1.age = 10;
  dog1.eat();//10岁的狗狗可以吃东西
 }
}

public class Animal {
 int age = 10;
 public Animal(){
  System.out.println("父类Animal执行了");
  age = 20;
 }
}
public class Dog extends Animal{
 public Dog(){
  System.out.println("子类Dog执行了");
 }
 public static void main(String[] args) {
  Animal a = new Animal();
  System.out.println(a.age);
  Dog dog1 = new Dog();
 }
}

public class Dog extends Animal{
 int age = 20;
 public void eat(){
  System.out.println(age+"岁的狗狗可以吃东西");
 }
 public Dog(){
  System.out.println("子类Dog执行了");
 }
 public void method(){
  super.eat();
 }
 public static void main(String[] args) {
  Dog dog1 = new Dog();
  dog1.method();//动物可以吃东西
 }
}

public class Dog extends Animal{
 int age = 20;
 public Dog(){
  super();//写与不写都一样，系统隐式调用
  System.out.println("子类Dog执行了");
 }
 public static void main(String[] args) {
  Dog dog1 = new Dog();
  //父类Animal执行了
  //子类Dog执行了
 }
}

public class Dog extends Animal{
 int age = 20;
 @Override
 public String toString() {
  return "Dog [age=" + age + "]";
 }
 public static void main(String[] args) {
  Dog dog1 = new Dog();
  System.out.println(dog1.toString());//未重写方法前的结果：Dog@15db9742
  System.out.println(dog1.toString());//Dog [age=20]
 }
}

public class Dog extends Animal{
 public static void main(String[] args) {
  Dog dog1 = new Dog();
  Dog dog2 = new Dog();
  if(dog1.equals(dog2)){
   System.out.println("两个对象相同");
  }else{
   System.out.println("两个对象不同");
  }
 }
}

public class Dog extends Animal{
 @Override
 public boolean equals(Object obj) {
  if (this == obj) //如果参数对象和当前对象相同，则一定相同
   return true;
  if (obj == null) //如果参数对象为空，则一定不同
   return false;
  if (getClass() != obj.getClass())//如果参数对象的类对象和当前对象的类对象不相等，则不相同
   return false;
  Dog other = (Dog) obj;//将参数进行强制转换
  if (age != other.age) //若属性值相等，则相同
   return false;
  return true;
 }
 public static void main(String[] args) {
  Dog dog1 = new Dog();
  dog1.age = 15;
  Dog dog2 = new Dog();
  dog2.age = 15;
  if(dog1.equals(dog2)){
   System.out.println("两个对象相同");
  }else{
   System.out.println("两个对象不同");
  }
 }
}