Java,Python,Scala比较（二）类与继承

UML图如下：

完整的Java代码如下：
SimpleGeometricObject.java

public class SimpleGeometricObject {    private String color = "white";    private boolean filled;    private java.util.Date dateCreated;    /**Construct a default geometric object */    public SimpleGeometricObject(){        dateCreated = new java.util.Date();    }    /**Construct a geometric object with the specified color     * and filled value*/    public SimpleGeometricObject(String color, boolean filled) {        dateCreated = new java.util.Date();        this.color = color;        this.filled = filled;    }    /**Return color*/    public String getColor() {        return color;    }    /**set a new color*/    public void setColor(String color) {        this.color = color;    }    /**Return filled. Since filled is boolean,     * its better method is named isFilled*/    public boolean isFilled() {        return filled;    }    /**Set a new filled*/    public void setFilled(boolean filled) {        this.filled = filled;    }    /**Get dateCreated*/    public java.util.Date getDateCreated(){        return dateCreated;    }    /**Return a string representation of this object*/    public String toString() {        return "created on "+dateCreated+"\ncolor: "+color+" and filled: "+filled;    }}

CircleFromSimpleGeometricObject.java

public class CircleFromSimpleGeometricObject extends SimpleGeometricObject{    private double radius;    public CircleFromSimpleGeometricObject() {}    public CircleFromSimpleGeometricObject(double radius) {        this.radius = radius;    }    public CircleFromSimpleGeometricObject(double radius, String color, boolean filled) {        super(color, filled);        this.radius = radius;       }    /**Return radius*/    public double getRadius() {        return radius;    }    /**Set a new radius*/    public void setRadius(double radius) {        this.radius = radius;    }    /**Return area*/    public double getArea() {        return radius*radius*Math.PI;    }    /**Return diameter*/    public double getDiameter() {        return 2*radius;    }    /**Return perimeter*/    public double getPerimeter() {        return 2*radius*Math.PI;    }    /**Return the circle info*/    public void printCircle() {        System.out.println("The circle is created "+getDateCreated()+" and the radius is "+radius);    }   }

RectangleFromSimpleGeometricObject.java

public class RectangleFromSimpleGeometricObject extends SimpleGeometricObject{    private double width;    private double height;    public RectangleFromSimpleGeometricObject() {}    public RectangleFromSimpleGeometricObject(double width, double height) {        this.width = width;        this.height = height;    }    public RectangleFromSimpleGeometricObject(double width, double height, String color, boolean filled) {        super(color, filled);        this.width = width;        this.height = height;    }    /**Return width*/    public double getWidth() {        return width;    }    /**Set a new width*/    public void setWidth(double width) {        this.width = width;    }    /**Return height*/    public double getHeight() {        return height;    }    /**Set a new width*/    public void setHeight(double height) {        this.height=height;    }       /**Return area*/    public double gerArea() {        return width*height;    }    /**Return perimeter*/    public double getPerimeter() {        return 2*(width+height);    }}

Test.java

public class Test{    public static void main(String[] args){        CircleFromSimpleGeometricObject circle = new CircleFromSimpleGeometricObject(1,"red", true);        System.out.println("A circle "+circle.toString());        System.out.println("The color is "+circle.getColor());        System.out.println("The radius is "+circle.getRadius());        System.out.println("The area is "+circle.getArea());        System.out.println("The diameter is "+circle.getDiameter());        RectangleFromSimpleGeometricObject rect = new RectangleFromSimpleGeometricObject(2,4);        System.out.println("\nA rectangle is "+rect.toString());        System.out.println("The area is "+rect.gerArea());        System.out.println("The perimeter is "+rect.getPerimeter());    }}

完整的Python代码如下：

import mathimport datetimeclass SimpleGeometricObject(object):    def __init__(self, color, filled):        self.__color = color        self.__filled = filled         self.__date = datetime.datetime.now()    def getColor(self):        return self.__color    def setColor(self, color):        self.__color = color    def isFilled(self):        return self.__filled    def setFilled(self, filled):        self.__filled = filled    def getDateCreated(self):        return self.__date.strftime("%Y/%m/%d/%H:%M")    def __str__(self):        return  "is created on "+self.getDateCreated()+", color: "+self.__color\                +" and filled: "+str(self.__filled)class CircleFromSimpleGeometricObject(SimpleGeometricObject):    def __init__(self, color, filled, radius):        super(CircleFromSimpleGeometricObject, self).__init__(color, filled)        self.__radius = radius    def getRadius(self):        return self.__radius    def setRadius(self, radius):        self.__radius = radius    def getArea(self):        return self.__radius*self.__radius*math.pi    def getPerimeter(self):        return 2*self.__radius*math.pi    def getDiameter(self):        return self.__radius*2    def printCircle(self):        print(self.__str__()+" and the radius is "+str(self.__radius))class RectangleFromSimpleGeometricObject(SimpleGeometricObject):    def __init__(self, color, filled, width, height):        super(RectangleFromSimpleGeometricObject, self).__init__(color, filled)        self.__width = width        self.__height = height    def getWidth(self):        return self.__width    def setWidth(self, width):        self.__width = width    def getHeight(self):        return self.__height    def setHeight(self, height):        self.__height = height     def getArea(self):        return self.__width * self.__height    def getPerimeter(self):        return 2*(self.__width+self.__height)def main():    circle = CircleFromSimpleGeometricObject("red", True, 5)    print("A circle ", circle)    print("The color is ", circle.getColor())    print("The radius is %s"%circle.getRadius())    print("The area is %s"%circle.getArea())    print("The diameter is %s"%circle.getDiameter())    rect = RectangleFromSimpleGeometricObject("white", False, 3, 4);    print("\nA rectangle", rect);    print("The area is %s"%rect.getArea());    print("The perimeter is %s"%rect.getPerimeter());main()

完整的Scala代码如下：

import java.util.Date;import scala.math._;object demo extends App {  class SimpleGeometricObject (private var color:String="white", private var filled:Boolean=false){    private var dateCreated:java.util.Date = new Date()    def getColor() = color    def setColor(color:String) = {this.color = color}    def isFilled() = filled    def setFilled(filled:Boolean) = {this.filled = filled}    def getDateCreated() = dateCreated     override def toString()= "created on "+dateCreated+"\ncolor: "+color+" and filled: "+filled  }  class CircleFromSimpleGeometricObject(color:String, filled:Boolean, private var radius:Double) extends SimpleGeometricObject(color,filled){    def this() = this("white", false, 1.0)    def getRadius() = radius    def setRadius(radius:Double) = {this.radius = radius}    def getArea() = radius*radius*Pi    def getDiameter() = radius*2    def getPerimeter() = radius*2*Pi    def printCircle() = {println("The circle is created "+getDateCreated+" and the radius is "+radius)}  }  class RectangleFromSimpleGeometricObject(color:String, filled:Boolean, private var width:Double, private var height:Double) extends SimpleGeometricObject(color, filled) {    def this() = this("white", false, 1.0, 1.0)    def getWidth() = width    def setWidth(width:Double) = {this.width = width}    def getHeight() = height    def setHeight(height:Double) = {this.height = height}    def getArea() = width*height    def getPerimeter() = 2*(width+height)  }  var circle = new CircleFromSimpleGeometricObject("red", true, 2.0)  println("A circle is "+circle.toString())  println("The color is "+circle.getColor())  println("The radius is "+circle.getRadius())  println("The area is "+circle.getArea())  println("The diameter is "+circle.getPerimeter())   var rect = new RectangleFromSimpleGeometricObject("green", true, 3.0, 4.0)  println("\nA rectangle is "+rect.toString())  println("The area is "+rect.getArea())  println("The perimeter is "+rect.getPerimeter())}

读者可以自己从上述代码中体验三种语言的相同点与不同之处，显然，Python与Scala语言较为简洁~~

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本次分享到此结束，欢迎大家交流~~