继承的概念和基本语法
定义:在原有类的基础上定义一个新类，原有类称为父类，新类称为子类。
class 子类名 extends 父类名 { 类体 }
好处:复用代码和实现多态。复用代码：子类可以继承父类的特性。多态： 子类可以在自己内部实现父类没有的特性
package level2
object Sc70 {
class Boss {
def power(): Unit = {
println("Boss 有权力....")
}
var car = "豪车"
}
class NoBody extends Boss {
}
def main(args: Array[String]): Unit = {
val b = new NoBody()
println(b.car)
b.power()
}
}
继承的方法重写
package level2
object Sc70 {
class Boss {
def power(): Unit = {
println("Boss 有权力....")
}
var car = "豪车"
}
class NoBody extends Boss {
def run():Unit = {
}
override def power():Unit = {
println("老莫，我想吃鱼了")
}
}
def main(args: Array[String]): Unit = {
val b = new NoBody()
println(b.car)
b.power()
b.run()
}
}
构造器的调用顺序
package level2
object Sc71 {
class Father() {
println("Father 构造器被调用")
}
class Son extends Father() {
println("Son 构造器被调用")
}
def main(args: Array[String]): Unit = {
new Son()
}
}
带参构造器的写法
package level2
object Sc72 {
class Dog(var name:String, var age:Int) {
println(s"Dog ${name}, ${age} 构造器被调用")
}
class RuralDog(name:String, age:Int) extends Dog(name, age) {
println("RuralDog 的构造器...")
}
def main(args: Array[String]): Unit = {
new RuralDog("旺财",3)
}
}
相比父类，子类有新属性
package level2
object Sc72 {
class Dog(var name:String, var age:Int) {
println(s"Dog ${name}, ${age} 构造器被调用")
}
class RuralDog(name:String, age:Int, var color:String) extends Dog(name, age) {
println(s"RuralDog 的构造器...${color}")
}
def main(args: Array[String]): Unit = {
new RuralDog("旺财",3,"土黄色")
}
}
