部分Java真题分析和总结.docx

Whichstatementistrue?

Ananonymousinnerclassmaybedeclaredasfinal.

Ananonymousinnerclasscanbedeclaredasprivate.

Ananonymousinnerclasscanimplementmultipleinterfaces.

Ananonymousinnerclasscanaccessfinalvariablesinanyenclosingscope.E.Constructionofaninstanceofastaticinnerclassrequiresaninstanceoftheenclosingouterclass.

答案是D

anonymousinnerclasscannotdeclaredwithanymodifyer.andcanonlyimplementoneinterface

Whichstatementaboutstaticinnerclassesistrue?A.Ananonymousclasscanbedeclaredasstatic

B.Astaticinnerclasscannotbeastaticmemberoftheouterclass

C.AstaticinnerclassdoesnotrequireaninstanceoftheenclosingclassD.Instancemembersofastaticinnerclasscanbereferencedusingtheclassnameofthestaticinnerclass

答案是C

becausestatic,itneedntinstanceofenclosingouterclassanditsinstancememberneeditsinstance.

publicclassFoo{

publicstaticvoidmain(Stringsgf[]){StringBuffera=newStringBuffer(A);StringBufferb=newStringBuffer(B);operate(a,b);System.out.println(a+,+b);

}

staticvoidoperate(StringBufferx,StringBuffery){x.append(y);

y=x;

}

}

Whatistheresult?

Thecodecompilesandprints“A.B”.

Thecodecompilesandprints“A.A”.

Thecodecompilesandprints“B.B”.

Thecodecompilesandprints“AB.B”.

Thecodecompilesandprints“AB.AB”.答案是D

java中都是按值传递的，所以a,b还是指向原来的地址空间，经过operate操作后，x更改了该地址空间的值，而y没有.

publicclassFoo{

publicstaticvoidmain(Stringsgf[]){StringBuffera=newStringBuffer(A);StringBufferb=newStringBuffer(B);

operate(a,b);//方法调用完以后，a对象的内容为：AB,b对象的内容为：BSystem.out.println(a+,+b);

}

staticvoidoperate(StringBufferx,StringBuffery){

//对象传递进来以后又分别复制了一个x和y对象x和y,x和x指向同一个对象。y和y指向同一个对象。

append(y);//所以执行此步操作以后，main中的x对象的内容也变化了。

//因为本来就是指向同一个对象吗！

y=x;//执行此步操作以后，main中的y对象的内容没变！

//因为此y费彼y也！

}

}

classValHold{

publicinti=10;

}

publicclassObParm{

publicstaticvoidmain(Stringargv[]){ObParm