实验3类与对象

（1）编写3个基本类：Triangle,Ladder和Circle，分别用来刻画“三角形”、“梯形”和“圆形”类；1个主类：Compute，负责计算每个形状的面积或周长。具体要求：定义3个变量：边长；和1个求周长的方法。定义3个变量：上底，下底和高；定义1个求面积的方法。定义1个变量：半径；定义2个方法：求面积、求周长。个基本类都要定义相应的构造方法，对变量进行初始化。packagetest3;classTriangle{doublea,b,c;publicTriangle(){}publicTriangle(doublea,doubleb,doublec){this.a=a;this.b=b;this.c=c;}publicdoubleC(){returna+b+c;}}classLadder{doubleup,down,height;publicLadder(){}publicLadder(doubleup,doubledown,doubleheight){this.up=up;this.down=down;this.height=height;}publicdoubleArea(){return(up+down)*height/2;}}classCircle{doubleradius;publicCircle(){}publicCircle(doubleradius){this.radius=radius;}publicdoubleArea(){returnMath.PI*radius*radius;}publicdoubleC(){returnMath.PI*radius*2.;}}publicclasstest3_a{publicstaticvoidmain(String[]args){Circlecc=newCircle(3);System.out.println(cc.Area());System.out.println(cc.C());Ladderld=newLadder(1,2,3);System.out.println(ld.Area());Triangletr=newTriangle(1,2,3);System.out.println(tr.C());}}（2）编写一个账户类Account，它包括：一个名为id的int型账号码属性，一个名为balance的double型的账号余额属性，定义一个类型为java.util.Date的属性dateCreated，用于记录账号的创建日期。同时，定义无参的构造函数，一个名为withDraw的方法从账号提取特定数目的金额，一个名为deposit的方法向账号存入特定数目的金额。请编写测试程序，测试各个方法。packagetest3;importjava.util.Calendar;importjava.util.Date;classAccount{intid;doublebalance;DatedateCreated;publicAccount(){}publicAccount(intid,doublebalance){this.id=id;this.balance=balance;this.dateCreated=(Date)Calendar.getInstance().getTime();}publicbooleanwithDraw(doublemoney){if(this.balancemoney){this.balance-=money;returntrue;}returnfalse;}publicvoiddeposit(doublemoney){this.balance+=money;}publicdoublegetBalance(){returnthis.balance;}}packagetest3publicclasstest_b{publicstaticvoidmain(String[]args){Accountac1=newAccount(12,100.);booleanresult=ac1.withDraw(1000);if(result)System.out.println(Success);else{System.out.println(Fail);ac1.deposit(1000);System.out.println(ac1.getBalance());}}}（3）编写一个封装学生的类Student，能够描述学生的“学号”、“姓名”、“性别”、“年龄”、“平均成绩”等基本属性，及获取属性、修改属性的方法和打印学生基本信息的print()方法。要求生成两个学生对象，在构造方法中进行初始化，并打印每个学生的基本信息。packagetest3;classStudent{privateintid;privateStringname;privatecharsex;privateintage;privatedoubleaverageScore;publicdoublegetAverageScore(){returnthis.averageScore;}publicvoidsetAverageScore(doublescore){this.averageScore=score;}publicStudent(){}publicStudent(intid,Stringname,charsex,intage,doublescore){this.id=id;this.name=name;this.sex=sex;this.age=age;this.averageScore=score;}publicvoidprint(){System.out.println(id++name++sex++age++averageScore);}}publicclasstest3_c{publicstaticvoidmain(String[]args){Studentst1=newStudent(1,zhang,'f',23,90);st1.print();st1.setAverageScore(80);st1.print();}}