Scala练习（十）

\1. java.awt.Rectangle类有两个很有用的方法translate和grow,但可惜的是像java.awt.geom.Ellipse2D这样的类没有。在Scala中，你可以解决掉这个问题。定义一个RenctangleLike特质,加入具体的translate和grow方法。提供任何你需要用来实现的抽象方法,以便你可以像如下代码这样混入该特质:

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val egg = new java.awt.geom.Ellipse2D.Double(5,10,20,30) with RectangleLikeegg.translate(10,-10)egg.grow(10,20)

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import java.awt.geom.Ellipse2Dtrait RectangleLike {  this: Ellipse2D.Double =>  def translate(x: Double, y: Double) {    this.x = x    this.y = y  }   def grow(x: Double, y: Double) {    this.x += x    this.y += y  }}object EclipseTest extends App {  val egg = new java.awt.geom.Ellipse2D.Double(5,10,20,30) with RectangleLike  egg.translate(10,-10)  egg.grow(10,20)  println(egg.getX)  println(egg.getY)}

\2. 通过把scala.math.Ordered[Point]混入java.awt.Point的方式，定义OrderedPoint类。按辞典编辑方式排序，也就是说，如果x\<x’或者x=x’且y\<y’则(x,y)\<(x’,y’)

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class OrderedPoint(x : Int, y : Int) extends java.awt.Point(x, y) with scala.math.Ordered[OrderedPoint]{  def compare(that : OrderedPoint) : Int = {    if (this.x == that.x && this.y == that.y) {      0    } else if ((this.x < that.x || this.x == that.x) && this.y < that.y) {      -1    } else {      1    }  }}object TestTrait extends App{  val test = Array(new OrderedPoint(3, 4), new OrderedPoint(4, 5));  scala.util.Sorting.quickSort(test)  test.foreach((p : OrderedPoint) => {println(p)})  val p1 = new OrderedPoint(3, 4);  val p2 = new OrderedPoint(4, 5);  println(p2 > p1)}

\3. 查看BitSet类,将它的所有超类和特质绘制成一张图。忽略类型参数([…]中的所有内容)。然后给出该特质的线性化规格说明

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\4. 提供一个CryptoLogger类，将日志消息以凯撒密码加密。缺省情况下密匙为3，不过使用者也可以重写它。提供缺省密匙和-3作为密匙是的使用示例

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trait Logger {  def log(str: String, key: Int = 3) : String}class CryptoLogger extends Logger {  def log(str: String, key: Int) : String = {    for ( i <- str) yield if (key >= 0) (97 + ((i - 97 + key)%26)).toChar else (97 + ((i - 97 + 26 + key)%26)).toChar  }}    object CryptoLoggerTest extends App {  val text = "nmred"  println(text)  println(new CryptoLogger().log(text))  println(new CryptoLogger().log(text, -3))}

\5. JavaBean规范里有一种提法叫做属性变更监听器(property change listener)，这是bean用来通知其属性变更的标准方式。PropertyChangeSupport类对于任何想要支持属性变更通知其属性变更监听器的bean而言是个便捷的超类。但可惜已有其他超类的类—比如JComponent—必须重新实现相应的方法。将PropertyChangeSupport重新实现为一个特质,然后将它混入到java.awt.Point类中

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import java.awt.Pointimport java.beans.PropertyChangeSupporttrait PropertyChange extends PropertyChangeSupportval p = new Point() with PropertyChange