特质 Trait

Trait 可堆叠特性

可自由组合你的算法，非常灵活。越靠后的特质越先执行。

特质使用的线性化解读 super

abstract class IntQueue {def get(): Int

      def put(x: Int)
    }

    class BasicIntQueue extends IntQueue {private val buf = new ArrayBuffer[Int]()

      override def get(): Int = buf.remove(0)

      override def put(x: Int): Unit = buf += x
    }

    trait Doubling extends IntQueue {abstract override def put(x: Int): Unit = super.put(2 * x)
    }

    trait Increming extends IntQueue {abstract override def put(x: Int): Unit = super.put(x + 1)
    }

    trait Filtering extends IntQueue {abstract override def put(x: Int): Unit = if (x > 0) super.put(x)
    }


    val myqueue1 = new BasicIntQueue with Doubling with Filtering with Increming
    myqueue1.put(1)
    println(myqueue1.get())

    val myqueue2 = new BasicIntQueue with Increming with Filtering with Doubling
    myqueue2.put(1)
    println(myqueue2.get())

    val myQueue = new BasicIntQueue with Doubling with Increming with Filtering
    myQueue.put(-1)
    println(myQueue.get())

要特质还是不要？

• 如果某个行为不会被复用
  用具体的类
• 如果某个行为可能被用于多个互不相关的类
  用特质，只有特质才能被混入类继承关系中位于不同组成部分的类
• 如果想从 Java 代码中继承某个行为
  用抽象类
• 上述问题都考虑之后，仍然没有答案
  试试特质吧