niusouti.com
publicclassPerson{2.privateStringname;3.publicPerson(Stringname){this.name=name;}4.publicbooleanequals(Personp){5.returnp.name.equals(this.name);6.}7.}Whichistrue?()A.TheequalsmethoddoesNOTproperlyoverridetheObject.equalsmethod.B.Compilationfailsbecauseth
题目
A.TheequalsmethoddoesNOTproperlyoverridetheObject.equalsmethod.
B.Compilationfailsbecausetheprivateattributep.namecannotbeaccessedinline5.
C.Toworkcorrectlywithhash-baseddatastructures，thisclassmustalsoimplementthehashCodemethod.
D.WhenaddingPersonobjectstoajava.util.Setcollection，theequalsmethodinline4willpreventduplicates.
相似考题
更多“publicclassPerson{2.privateStringname;3.publicPerson(Stringname){this.name=name;}4.publicbooleanequals(Personp){5.returnp.name.equals(this.name);6.}7.}Whichistrue?() ”相关问题
-
第1题：
Giventhismethodinaclass:publicStringtoString(){StringBufferbuffer=newStringBuffer();buffer.append(?<?);buffer.append(this.name);buffer.append(?>?);returnbuffer.toString();}Whichistrue?()A.ThiscodeisNOTthread-safe.
B.TheprogrammercanreplaceStringBufferwithStringBuilderwithnootherchanges.
C.ThiscodewillperformwellandconvertingthecodetouseStringBuilderwillnotenhancetheperformance.
D.Thiscodewillperformpoorly.Forbetterperformance，thecodeshouldberewritten：return“<“+this.name+“>”；
参考答案：B
-
第2题：
publicclassPerson{privatename;publicPerson(Stringname){this.name=name;}publicinthashCode(){return420;}}Whichistrue?()A.ThetimetofindthevaluefromHashMapwithaPersonkeydependsonthesizeofthemap.
B.DeletingaPersonkeyfromaHashMapwilldeleteallmapentriesforallkeysoftypePerson.
C.InsertingasecondPersonobjectintoaHashSetwillcausethefirstPersonobjecttoberemovedasaduplicate.
D.ThetimetodeterminewhetheraPersonobjectiscontainedinaHashSetisconstantanddoesNOTdependonthesizeofthemap.
参考答案：A
-
第3题：
Person p = new Person(“张三”,23);这条语句会调用下列哪个构造方法给属性进行初始化()A.public Person(){}
B.public Person(String name,int age) { this.name = name; this.age = age; }
C.public Person(int age,String name) { this.age = age; this.name = name; }
D.public Person(String name) { this.name = name; }
答案：B
解析：创建对象时会找到匹配的构造方法给属性进行初始化，由于Person p = new Person(“张三”,23);这条语句中有两个参数，而且第1个参数是String类型的，第2个参数是int类型的，因此会调用B选项中的构造方法。
-
第4题：
publicclassPlant{privateStringname;publicPlant(Stringname){this.name=name;}publicStringgetName(){returnname;}}publicclassTreeextendsPlant{publicvoidgrowFruit(){}publicvoiddropLeaves(){}}Whichistrue?()A.Thecodewillcompilewithoutchanges.
B.ThecodewillcompileifpublicTree（）{Plant（）；}isaddedtotheTreeclass.
C.ThecodewillcompileifpublicPlant（）{Tree（）；}isaddedtothePlantclass.
D.ThecodewillcompileifpublicPlant（）{this（”fern”）；}isaddedtothePlantclass.
E.ThecodewillcompileifpublicPlant（）{Plant（”fern”）；}isaddedtothePlantclass.
参考答案：D
-
第5题：
interface Playable {
void play();
}
interface Bounceable {
void play();
}
interface Rollable extends Playable, Bounceable {
Ball ball = new Ball("PingPang");
}
class Ball implements Rollable {
private String name;
public String getName() {
return name;
}
public Ball(String name) {
this.name = name;
}
public void play() {
ball = new Ball("Football");
System.out.println(ball.getName());
}
}
这个错误不容易发现。
正确答案：错。"interface Rollable extends Playable, Bounceable"没有问题。interface 可继承多个
interfaces，所以这里没错。问题出在interface Rollable 里的"Ball ball = new Ball("PingPang");"。
任何在interface 里声明的interface variable (接口变量，也可称成员变量)，默认为public static
final。也就是说"Ball ball = new Ball("PingPang");"实际上是"public static final Ball ball = new
Ball("PingPang");"。在Ball 类的Play()方法中，"ball = new Ball("Football");"改变了ball 的
reference，而这里的ball 来自Rollable interface，Rollable interface 里的ball 是public static final
的，final 的object 是不能被改变reference 的。因此编译器将在"ball = new Ball("Football");"
这里显示有错。