30道英文Java面试题附英文答案(1-15) .pdfVIP

内容摘要：如果你打算参加IT外企的java软件工程师面试的话，本文你点详细

研读一下。软件开发行业的外企面试一般都是全英文哦（技术面试和非技术面试）。

内容正文：

*Q1.HowcouldJavaclassesdirectprogrammessagestothesystemconsole,

buterrormessages,saytoafile?.

TheclassSystemhasavariableoutthatrepresentsthestandardoutput,

andthevariableerrthatrepresentsthestandarderrordevice.Bydefault,

theybothpointatthesystemconsole.Thishowthestandardoutputcould

bere-directed:

Streamst=newStream(newFileOutputStream(output.txt));

System.setErr(st);System.setOut(st);

*Q2.Whatsthedifferencebetweenaninterfaceandanabstractclass?

A.Anabstractclassmaycontaincodeinmethodbodies,whichisnot

allowedinaninterface.Withabstractclasses,youhavetoinherityour

classfromitandJavadoesnotallowmultipleinheritance.Ontheother

hand,youcanimplementmultipleinterfacesinyourclass.

*Q3.Whywouldyouuseasynchronizedblockvs.synchronizedmethod?

A.Synchronizedblocksplacelocksforshorterperiodsthansynchronized

methods.

*Q4.Explaintheusageofthekeywordtransient?

A.Thiskeywordindicatesthatthevalueofthismembervariabledoesnot

havetobeserializedwiththeobject.Whentheclasswillbede-serialized,

thisvariablewillbeinitializedwithadefaultvalueofitsdatatype

(i.e.zeroforintegers).

*Q5.Howcanyouforcegarbagecollection?

A.YoucantforceGC,butcouldrequestitbycallingSystem.gc().JVM

doesnotguaranteethatGCwillbestartedimmediately.

*Q6.Howdoyouknowifanexplicitobjectcastingisneeded?

A.Ifyouassignasuperclassobjecttoavariableofasubclasssdata

type,youneedtodoexplicitcasting.Forexample:

Objecta;Customerb;b=(Customer)a;

Whenyouassignasubclasstoavariablehavingasupeclasstype,the

castingisperformedautomatically.

*Q7.Whatsthedifferencebetweenthemethodssleep()andwait()

A.Thecodesleep(1000);putsthreadasideforexactlyonesecond.