姓名年级院系专业学号西北大学2005----2006学年第2学期本科考试出题专用纸考试科目《Java程序设计》总分Objectsofasubclasscanbetreatedlikeobjectsoftheirsuperclass.Noneoftheabove.7.Considertheabstractsuperclassbelow:publicabstractclassFoo{privateinta;publicintb;publicFoo(intaVal,intbVal){a=aVal;b=bVal;}publicabstractintcalculate();}AnyconcretesubclassthatinheritsfromclassFoo:Mustimplementamethodcalledcalculate().Willnotbeabletoaccesstheinstancevariablea.WillnotbeabletoinstantiateanobjectofclassFoo.Alloftheabove.8.WhichofthefollowingisnotavalidconstructorforaJLabel?JLabel(int,horizontalAlignment,Iconimage);JLabel(Iconimage);JLabel(Stringtext,Iconimage,inthorizontalAlignment);JLabel(Stringtext,inthorizontalAlignment);9.WhichofthefollowingstepsisnotrequiredtouseaJLabelasaGUIcomponent?DeclareareferencetoaJLabel.AddtothecontentPane().InstantiatetheJLabel.InitializetheJLabeltext.10.WhichofthefollowingstatementsaboutJTextFieldsandJPasswordFieldsisnottrue?AJTextFieldisaJTextComponent.AJTextFieldisaJPasswordField.JPasswordField(Stringtext,intcolumns)isavalidconstructor.JTextField(Stringtext,intcolumns)isavalidconstructor.11.JTextFieldandJPasswordFieldeventsarehandledusingwhichinterfaces?BothusetheActionListenerinterface.BothusetheTextFieldListenerinterface.BothusetheTextComponentListenerinterface.TheyuseTextFieldListenerandActionListenerinterfacesrespectively.12.ThemethodsetRolloverIconisusedto:Handleamouseevent.Changethebuttontext.Changethebuttonicon.Alloftheabove.注意：答案必须写在统一配发的答题纸上。本试卷满分70分，平时成绩30分。一、SingleChoice(每小题1.5分，共30)1.Whichstatementbelowcouldbeusedtosimulatetheoutputsoftossingaquartertogetheadsortails?1+(int)(Math.random()*6);1+(int)(Math.random()*2);6+(int)(Math.random()*1);1+(int)(Math.random()*25);2.AJButtoncancauseanevent(i.e.,acalltoanevent-handlingmethod)if:Aneventhandlerhasbeencalled.TheregisteredeventhandlerimplementstheActionListenerinterface.TheregisteredeventhandlerextendstheGUI.TheJButtonhasbeenaddedtoJApplet.3.AJavaclasscanhavewhichofthefollowingm