實(shí)驗(yàn) 抽象類和接口實(shí)驗(yàn)報(bào)21請(qǐng)?jiān)O(shè)計(jì)3個(gè)類分別是學(xué)生類Student，本科生類Undergraduate和類Postgraduate，其中Student類是一個(gè)抽象類它包含了一些學(xué)生基本信息如所學(xué)課程課程成績(jī)等，5060s，個(gè)類InterfaceTest，在這個(gè)類中定義一個(gè)字符串類型的變量message，重寫speakmessage方式下編譯好程序之后，在運(yùn)行程序時(shí)輸入java 實(shí)驗(yàn)一classStudent{Stringname;Stringtype;intgrade;Stringlevel;Stringcnt(int}classUndergraduateextendsStudent{Stringcnt(intgrade){if(grade>=80&&grade<=100return"優(yōu)秀";if(grade>=70&&grade<=79)return"良好";if(grade>=60&&grade<=69)return"一般";if(grade>=50&&grade<=59)return"及格";return"不及格";}}classPostgraduateextendsStudent{Stringcnt(intgrade){if(grade>=90&&grade<=100return"優(yōu)秀";if(grade>=80&&grade<=89)return"良好";if(grade>=70&&grade<=79)return"一般";if(grade>=60&&grade<=69)return"及格";return"不及格";}}publicclassPolymorphismpublicstaticvoidmain(String[]args){Undergraduateunder=newUndergraduate();Postgraduatepost=newPostgraduate();System.out.println("類型成績(jī) 等級(jí)"); Student[]stu=newStudent[5];stu[0]=newUndergraduate();stu[0].name="";stu[0].gradeSystem.out.print(stu[0].name+""+stu[0].type+""+stu[0].grade+"if(stu[0].type本科生 if(stu[0].type==" stu[1]=newUndergraduate();stu[1].name魯向東stu[1].grade=82;System.out.print(stu[1].name+""+stu[1].type+""+stu[1].grade+""); stu[2]=newPostgraduate();stu[2].name="";stu[2].grade=81;System.out.print(stu[2].name+""+stu[2].type+""+stu[2].grade+""); stu[3]=newUndergraduate();stu[3].name="";stu[3].gradeSystem.out.print(stu[3].name+""+stu[3].type+""+stu[3].grade+""); stu[4]=newPostgraduate();stu[4].name="";stu[4].grade=86;System.out.print(stu[4].name+""+stu[4].type+""+stu[4].grade+""); }}interfacevoidspeakmessage(String}classAimplementspublicvoidspeakmessage(String}}publicclassInterfaceTestpublicstaticvoidmain(