Scala的Set集合

直裾2024-11-17 17:48

复制代码

//设置一个Book。有三个属性：书名，作者，价格
class Book(var bookNmame:String,var author:String,var price:Double){}
object demo7 {
  def main(args: Array[String]): Unit = {
//    val set1 = Set(1,1,2,3,3)
//    println(set1)
    //创建可变S儿童，添加两本相同的书
    val set1 = scala.collection.mutable.Set[Book]()

    val book1 = new Book("西游记","吴承恩",100)
    val book2 = new Book("西游记","吴承恩",100)

    println(book1 == book2)

    set1 += book1
    set1 += book2

    //问题：Set可以把两本相同的书。做去重处理吗？
    set1.foreach(s =>{
      println(s.author)
    })
  }
}

//Set:特点去重
//设置一个Book。有三个属性：书名，作者，价格
class Book(var bookName:String,var author:String,var price:Double){
  override def equals(obj: Any): Boolean = {
    //判断依据是书名相同
    val o = obj.asInstanceOf[Book]
    o.bookName == bookName
  }

  override def toString: String = s"书名是:$bookName,作者:$author,价格:$price"

  override def hashCode(): Int = bookName.hashCode()
}
//case class 的特点
//1，数据是只读的
//2，可以省略new
//3，它内置实现了一些方法
//equals hashCode ,toString
case class BookCase(bookName:String,author:String,price:Double)

object demo8 {
  def main(args: Array[String]): Unit = {

    val book1 = new Book("a","a",1)
    val book11 = new Book("a","a",1)

    val set1 = Set(book1,book11)

    println(set1)

    val book2 = BookCase("a","a",1)
    val book3 = BookCase("a","a",1)

    println(book1 == book11)
    println(book2 == book3)

    println(book1)// println会自动去调用对象的toString方法
    println(book2)
  }
}

1：case class的定义语法是什么？

case class 类名(属性名:类型,属性名:类型)

2：case class的特点？

它的属性值不能被修改

可以不写new

内置了toString，equals，hashCode特别适用于来定义数据格式