Java继承与多态.ppt

第5章第5章继承和多态继承性与多态性是面向对象程序设计的另外两个重要特性。在Java语言中，提供了能够实现继承性与多态性的完备技术，这使得更多的人们愿意将Java作为软件开发语言，进而充分地施展面向对象抽象性、封装性、继承性与多态性的优势，为构筑新时代的软件开发理念奠定了坚固基础。目录5.1类的继承继承关系的UML图形符号表示法5.1.1定义子类EmployeeClass类与ManagerClass类的关系图//filename：EmployeeClass.java
publicclassEmployeeClass{//雇员类
privateStringname; //姓名
privatedoublesalary; //工资
privateStringdepartment; //部门
publicEmployeeClass(){...}
publicEmployeeClass(Stringname,
doublesalary,Stringdepartment){...}
publicvoidsetName(Stringname){...}
publicvoidsetSalary(doublesalary){...}
publicvoidsetDepartment(Stringdepartment){...}
publicStringgetName(){...}
publicdoublegetSalary(){...}
publicStringgetDeparyment(){...}
publicStringtoString(){...}
}publicManagerClassextendsEmployeeClass{//经理类
privatedoublespecial;//特殊津贴
publicManagerClass(){...}
publicManagerClass(Stringname,doublesalary,
Stringdepartment,doublespecial){...}
publicvoidsetSpecial(doublespecial){...}
publicdoublegetSpecial(){...}
publicStringtoString(){...}
}举例：设计与几何图元有关的类。ShapeClass类、RectangleClass类与SquareClass类之间的关系类图//filename：ShapeClass.java
importjava.util.*;
publicclassShapeClass{ //几何图元类
privateColorClasscolor; //颜色属性
privatePointplace; //位置属性
publicShapeClass(){
color=newColorClass();
place=newPoint();
}
publicShapeClass(ColorClasscolor,Pointplace){
this.color=color;
this.place=place;
}
publicvoidsetColor(ColorClasscolor){this.color=color;}
publicvoidsetPlace(Pointplace){this.place=place;}
publicColorClassgetColor(){returncolor;}
publicPointgetPlace(){returnplace;}
publicStringtoString(){
returncolor.toString()+"\n"+place.toString();
}
}//filename：RectangleClass.java
publicclassRectangleClassextendsShapeClass{//矩形类
privateintlength; //长
privateintwidth; //宽
publicRectangleClass(){
super();length=0;width=0;
}
publicRectangleClass(ColorClasscolor,Pointplace,intlength,intwidth){
super(color,place);this.length=length;this.width=width;
}
publicintarea(){returnlength*width;}//计算矩形的面积
publicintpermeter(){return2*(length*width);} //计算矩形的周