JAVA程序员笔到试题目与答案.doc

1. Given:? Integer?i?=?new?Integer?(42); Long?l?=?new?Long?(42); Double?d?=?new?Double?(42.0);? Which?two?expressions?evaluate?to?True? A.?(i?==?1) B.?(i?==?d) C.?(d?==?1) D.?(i.equals?(l)) E.?(d.equals?(l)) F.?(i.equals?(42))? G.?none?of?above Answer:?????????? ? 2.?Given:? public?class?Foo?{ ????public?static?void?main?(String?[]?args)??{ ????????StringBuffer?a?=?new?StringBuffer(A); ????????StringBuffer?b?=?new?StringBuffer?(B); ????????operate?(a,b); ????????System.out.println(a?+?,?+b); ????} ????static?void?operate(StringBuffer?x,?StringBuffer?y)?{ ????????x.append(y); ????????y?=?x; ????} } What?is?the?result?? A.?The?code?compiles?and?prints?“A,B”. B.?The?code?compiles?and?prints?“A,A”. C.?The?code?compiles?and?prints?“B,B”. D.?The?code?compiles?and?prints?“AB,B”. E.?The?code?compiles?and?prints?“AB,AB”. F.?The?code?does?not?compile?because?“+”?cannot?be?overloaded?for?StringBuffer.? Answer:???????? ? ? 3.Given: class?BaseClass?{ ????private?float?x?=?1.0f?; ????protected?float?getVar()?{return?x;} } class?Subclass?extends?BaseClass?{ ????private?float?x?=?2.0f; ????//insert?here } Which?two?are?valid?examples?of?method?overriding? A.?float?getVar()?{?return?x;} B.?public?float?getVar()?{?return?x;} C.?public?double?getVar()?{?return?x;} D.?protected?float?getVar()?{?return?x;} E.?public?float?getVar(float?f)?{?return?f;} Answer:??????? ? 4.?Which?of?the?following?are?methods?of?the?Runnable?interface A)?run B)?start C)?yield D)?stop Answer:???????????? ? 5.?Which?of?the?following?are?legal?statements? A)?float?f=1/3; B)?int?i=1/3; C)?float?f=1.01; D)?double?d=999d; Answer:???????????????? ? 6.?Given: public?class?test( ????public?static?void?main(string[]?args){ ????????String?foo?=?args[1]; ????????String?baz?=?args[2]; ????????String?bax?=?args[3]; ????} }? And?the?command?line?invocation:? Java?Test?red?green?blue? What?is?the?result?? A.?baz?has?the?value?of?“” B.?baz?has?th