JAVA认证历年真题：SCJP考试真题和解析.pdf

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1、JAVA认证历年真题：SCJP考试真题和解析(1)JAVA认证历年真题：SCJP考试真题和解析例题1：Choose the three valid identifiers from those listed below.A.IDoLikeTheLongNameCiassB.$byteC.constD._okE.3_case解答：A,B,D点评：Jav a中的标示符必须是字母、美元符($)或下划线(_)开头。关键字与保留字不能作为标示符。选项C 中的const是 Java的保留字，所以不能作标示符。选项E 中的3_case以数字开头，违反了 Java的规则。例题2：How can you for

2、ce garbage collection of an object?A.Garbage collection cannot be forcedB.Call System.gc().C.Call System.gc(),passing in a reference to the object to be garbage collected.D.Call Runtime.gc().E.Set all references to the object to new values(null,for example).解答：A点评：在 Java中垃圾收集是不能被强迫立即执行的。调用System.gc(

3、)或 Runtime.gc。静态方法不能保证垃圾收集器的立即执行，因为，也许存在着更高优先级的线程。所以选项B、D 不正确。选 项 C 的错误在于，System.gc。方法是不接受参数的。选 项 E 中的方法可以使对象在下次垃圾收集器运行时被收集。例题3：Consider the following class:1.class Test(int i)2.void test(int i)3.System.out.println(4tI am an int.);4.)5.void test(String s)6.System.out.printlnCI am a string.);7.8.9.pu

4、blic static void main(String args)10.Test t=new Test();l l.c h a rc h ;12.t.test(ch);13.14.Which of the statements below is true?(Choose one.)A.Line 5 will not compile,because void methods cannot be overridden.B.Line 12 will not compile,because there is no version of test()that rakes a char argument

5、.C.The code will compile but will throw an exception at line 12.D.The code will compile and produce the following output:I am an int.E.The code will compile and produce the following output:I am a String.解答：D点评：在 第 12行，16位长的char型变量ch在编译时会自动转化为一个32位长的int型,并在运行时传给void test(int i)方法。Question No:1Given:

6、1.public class test(2.public static void main(String args)3.inti=OxFFFFFFFl;4.int j=i;5.6.7.)What is the decimal value of j at line 5?A.OB.1C.14D.-15E.An error at line 3 causes compilation to fail.F.An error at line 4 causes compilation to fail.Answer:DQuestion No:2Given:Integer i=new Integer(42);Lo

7、ng 1 =new Long(42);Double d=new Double(42.0);Which two expressions evaluate to True?(Choose Two)A.(i=1)B.(i=d)C.(d=1)D.(i.equals(d)E.(d.equals(i)F.(i.equals(42)Answer:D,EQuestion No:3Exhibit:1.public class test(2.private static int j=0;3.4.private static boolean methodB(int k)(5.j+=k;6.return true;6

8、.)7.8.public static void methodA(int i)9.boolean b:10.b=i<lOlmethodB(4);l l.b=i<1011 methodB(8);12.)13.14.public static void main(String args(15.methodA(0);16.system.out.println(j);17.)18.)What is the result?A.The program prints A”B.The program prihat is the output?Answer:5Question No:5Given:1

9、.public class Foo 2.public static void main(String args)3.StringBuffer a=new StringBuffer();4.StringBuffer b=new StringBuffer(B”)；5.operate(a,b);6.system.out.printlna+b);7.)8.static void operate(StringBuffer x,StringBuffer y)9.x.append y;10.y=x;11.)12.)What is the result?A.The code compiles and prin

10、tsB.The code compiles and prints A,A”.C.The code compiles and printsD.The code compiles and printsE.The code compiles and prints AB,AB”.F.The code does not compile because cannot be overloaded for StringBuffer.Answer:D IIIQuestion No:6Exhibit:1.Public class test(2.Public static void stringReplace(St

11、ring text)(3.Text=text.replace(j,i)；4.)5.6.public static void bufferReplace(StringBuffer text)(7.text=text.append(“C”)8.)9.10.public static void main(String args)(11.String textString=new String(java);12.StringBuffer text BufferString=new StringBuffer(“java”)；13.14.stringReplace(textString);15.Buffe

12、rReplace(textBuffer);16.17.System.out.printin(textString+textBuffer);18.19.)What is the output?Answer:javajavaCQuestion No:7Exhibit:1.public class test 2.public static void add3(Integer i)3.int val=i.intValue();4.val+=3;5.i=new Integer(val);6.)7.8.public static void main(String args )9.Integer i=new

13、 Integer(0);10.add3(i);11.system.out.println(i.intValue();12.)13.)What is the result?A.Compilation will fail.B.The program prints 0.C.The program prints 3”.D.Compilation will succeed but an exception will be thrown at line 3.Answer:BQuestion No:8Given:1.public class ConstOver 2.public ConstOver(int

14、x,int y,int z)3.4.)Which two overload the ConstOver constructor?(Choose Two)A.ConstOver()B.Protected int ConstOver()C.Private ConstOver(int z,int y,byte x)D.Public Object ConstOver(int x,int y,int z)E.Public void ConstOver(byte x,byte y,byte z)Answer:A,CQuestion No:9Given:1.public class MethodOver 2

15、.public void setVar(int a,int b,float c)3.)4.Which two overload the setVar method?(Choose Two)A.Private void setVar(int a,float c,int b)B.Protected void setVar(int a,int b,float c)C.Public int setVar(int a,float c,int b)(return a;)D.Public int setVar(int a,int b,float c)(return a;)E.Protected float

16、setVar(int a,int b,float c)(return c;)Answer:A,CQuestion No:10Given:1.class BaseClass 2.Private float x=l.Of;3.protected float getVar()(return x;)4.)5.class Subclass extends BaseClass(6.private float x=2.0f;7./insert code here8.)Which two are valid examples of method overriding?(Choose Two)A.Float g

17、etVar()return x;B.Public float getVar()return x;C.Float double getVar()return x;D.Public float getVar()return x;E.Public float getVar(float f)return f;Answer:B,DQuestion No:11Which two demonstrate an is a,5 relationship?(Choose Two)A.public interface Person public class Employee extends Person B.pub

18、lic interface Shape public class Employee extends Shape C.public interface Color public class Employee extends Color D.public class Species public class Animal(private Species species;)E.interface Component Class Container implements Component(Private Component1 children;)Answer:D,EQuestion No:12Whi

19、ch statement is true?A.An anonymous inner class may be declared as final.B.An anonymous inner class can be declared as private.C.An anonymous inner class can implement multiple interfaces.D.An anonymous inner class can access final variables in any enclosing scope.E.Construction of an instance of a

20、static inner class requires an instance of the enclosing outerclass.Answer:D IIIQuestion No 13Given:1.package foo;2.3.public class Outer(4.public static class Inner(5.)6.)Which statement is true?A.An instance of the Inner class can be constructed with“new Outer.Inner()”B.An instance of the inner cla

21、ss cannot be constructed outside of package foo.C.An instance of the inner class can only be constructed from within the outer class.D.From within the package bar,an instance of the inner class can be constructed with”newinner。Answer:AQuestion No 14Exhibit:1.public class enclosingone(2.public class

22、insideone3.)4.public class inertest(5.public static void main(stringargs)(6.enclosingone eo=new enclosingone();7./insert code here8.)9.)Which statement at line 7 constructs an instance of the inner class?A.InsideOnew ei=eo.new InsideOn();B.Eo.InsideOne ei=eo.new InsideOne();C.InsideOne ei=EnclosingO

23、ne.new InsideOne();D.EnclosingOne.InsideOne ei=eo.new InsideOne();Answer:DQuestion No 15Exhibit:1.interface foo 2.int k=0;3.4.5.public class test implements Foo(6.public static void main(String args)(7.int i;8.Test test=new test();9.i=test.k;10.i=Test.k;1 l.i=Foo.k;12.)13.)14.What is the result?A.Co

24、mpilation succeeds.B.An error at line 2 causes compilation to fail.C.An error at line 9 causes compilation to fail.D.An error at line 10 causes compilation to fail.E.An error at line 11 causes compilation to fail.Answer:AQuestion No 16Given:1./point X2.public class foo(3.public static void main(Stringargs)throws Exception