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. IDoLikeTheLongNameClass B. $byte C. const D. _ok E. 3_case 解答：A, B, D

点评：Java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 force garbage collection of an object? A. Garbage collection cannot be forced B. 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()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(“I am an int.”); 4. }

5. void test(String s) {

6. System.out.println(“I am a string.”);

7. } 8.

9. public static void main(String args) {

10. Test t=new Test(); 11. char ch=“y”; 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.

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: 1 Given:

1. public class test (

2. public static void main (String args) { 3. int i = 0xFFFFFFF1; 4. int j = ~i; 5. 6. } 7. )

What is the decimal value of j at line 5? A. 0 B. 1 C. 14 D. –15

E. An error at line 3 causes compilation to fail. F. An error at line 4 causes compilation to fail. Answer: D

Question No: 2 Given:

Integer i = new Integer (42); Long 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, E Question No: 3 Exhibit :

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. ) 7.

8. public static void methodA(int i) { 9. boolean b:

10. b = i < 10 | methodB (4); 11. b = i < 10 || methodB (8); 12. ) 13.

14. public static void main (String args } ( 15. methodA (0);

16. system.out.printIn(j); 17. ) 18. )

What is the result?

A. The program prints “0” B. The program prints “4” C. The program prints “8” D. The program prints “12” E. The code does not complete. Answer: B Question No: 4 Given

1. Public class test (

2. Public static void main (String args) ( 3. System.out.printIn (6 ^ 3); 4. ) 5. )

What is the output? Answer: 5 Question No: 5 Given:

1. public class Foo {

2. public static void main (String args) { 3. StringBuffer a = new StringBuffer (“A”); 4. StringBuffer b = new StringBuffer (“B”); 5. operate (a,b);

6. system.out.printIn{a + “,” +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 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: D ||| Question No: 6 Exhibit:

1. Public class test (

2. Public static void stringReplace (String 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. BufferReplace (textBuffer); 16.

17. System.out.printIn (textString + textBuffer); 18. } 19. )

What is the output? Answer: javajavaC Question No: 7 Exhibit:

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 Integer (0); 10. add3 (i);

11. system.out.printIn (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: B Question No: 8 Given:

1. public class ConstOver {

2. public ConstOver (int 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, C Question No: 9 Given:

1. public class MethodOver {

2. 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 setVar (int a, int b, float c) (return c;) Answer: A, C Question No: 10 Given:

1. class BaseClass { 2. Private float x = 1.0f ;

3. protected float getVar ( ) ( return x;) 4. }

5. class Subclass extends BaseClass ( 6. private float x = 2.0f; 7. //insert code here 8. )

Which two are valid examples of method overriding? (Choose Two) A. Float getVar ( ) { 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, D Question No: 11

Which two demonstrate an “is a” relationship? (Choose Two) A. public interface Person { }

public class Employee extends Person { } B. public 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 Component[ ] children; )

Answer: D, E Question No: 12

Which 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 static inner class requires an instance of the enclosing outer class.

Answer: D ||| Question No 13 Given:

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 class 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 “new inner()” Answer: A

Question No 14

Exhibit:

1. public class enclosingone ( 2. public class insideone{} 3. )

4. public class inertest(

5. public static void main (stringargs)( 6. enclosingone eo= new enclosingone (); 7. //insert code here 8. ) 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 = EnclosingOne.new InsideOne(); D. EnclosingOne.InsideOne ei = eo.new InsideOne(); Answer: D Question No 15 Exhibit:

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; 11.i= Foo.k; 12.) 13.) 14.

What is the result?

A. Compilation 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: A

Question No 16 Given: 1. //point X

2. public class foo (

3. public static void main (Stringargs) throws Exception {

4. printWriter out = new PrintWriter (new

5. java.io.outputStreamWriter (System.out), true; 6. out.printIn(“Hello”); 7. } 8. )

Which statement at PointX on line 1 allows this code to compile and run? A. Import java.io.PrintWriter; B. Include java.io.PrintWriter;

C. Import java.io.OutputStreamWriter; D. Include java.io.OutputStreamWriter; E. No statement is needed. Answer: A

Question No 17

Which two statements are reserved words in Java? (Choose Two) A. Run B. Import C. Default D. Implement Answer: B, C Question No 18

Which three are valid declarations of a float? (Choose Three) A. Float foo = -1; B. Float foo = 1.0; C. Float foo = 42e1; D. Float foo = 2.02f; E. Float foo = 3.03d; F. Float foo = 0x0123; Answer: A, D, F

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Question No 19 Given:

8. int index = 1;

9. boolean test = new Boolean; 10. boolean foo= test [index]; What is the result?

A. Foo has the value of 0. B. Foo has the value of null. C. Foo has the value of true. D. Foo has the value of false. E. An exception is thrown. F. The code will not compile. Answer: D

Question No 20 Given:

1. public class test(

2. public static void main(stringargs){ 3. string foo = args [1]; 4. string foo = args ; 5. string foo = args ; 6. } 7. }

And command line invocation: Java Test red green blue What is the result?

A. Baz has the value of “” B. Baz has the value of null C. Baz has the value of “red” D. Baz has the value of “blue” E. Bax has the value of “green” F. The code does not compile.

G. The program throws an exception. Answer: G

Question No 21 Given:

8. int index = 1;

9. int foo = new int ; 10.int bar = foo [index]; 11.int baz = bar + index; What is the result?

A. Baz has the value of 0 B. Baz has the value of 1 C. Baz has the value of 2 D. An exception is thrown. E. The code will not compile. Answer: B

Question No 22 Given:

1. public class foo {

2. public static void main (Stringargs) { 3. String s;

4. system.out.printIn (“s=” + s); 5. } 6. }

What is the result?

A. The code compiles and “s=” is printed.

B. The code compiles and “s=null” is printed.

C. The code does not compile because string s is not initialized. D. The code does not compile because string s cannot be referenced. E. The code compiles, but a NullPointerException is thrown when toString is called. Answer: C

Question No 23

Which will declare a method that forces a subclass to implement it? A. Public double methoda();

B. Static void methoda (double d1) {} C. Public native double methoda(); D. Abstract public void methoda();

E. Protected void methoda (double d1){} Answer: D

Question No 24

You want subclasses in any package to have access to members of a superclass. Which is the most

restrictive access modifier that will accomplish this objective? A. Public B. Private C. Protected D. Transient

E. No access modifier is qualified Answer: C

Question No 25 Given:

1. abstract class abstrctIt { 2. abstract float getFloat (); 3. )

4. public class AbstractTest extends AbstractIt { 5. private float f1= 1.0f;

6. private float getFloat () {return f1;} 7. }

What is the result?

A. Compilation is successful.

B. An error on line 6 causes a runtime failure. C. An error at line 6 causes compilation to fail. D. An error at line 2 causes compilation to fail. Answer: C

Question No 26 Exhibit:

1. public class test( 2. public int aMethod()[ 3. static int i=0; 4. i++;

5. return I; 6. )

7. public static void main (String args){ 8. test test = new test(); 9. test.aMethod();

10.int j = test.aMethod(); 11.System.out.printIn(j); 12.] 13.}

What is the result?

A. Compilation will fail.

B. Compilation will succeed and the program will print “0” C. Compilation will succeed and the program will print “1” D. Compilation will succeed and the program will print “2” Answer: D ||| Question No 27 Given:

1. class super {

2. public float getNum() {return 3.0f;} 3. ) 4.

5. public class Sub extends Super { 6. 7. )

Which method, placed at line 6, will cause a compiler error? A. Public float getNum() {return 4.0f; } B. Public void getNum () { }

C. Public void getNum (double d) { }

D. Public double getNum (float d) {retrun 4.0f; } Answer: B

Question No 28

Which declaration prevents creating a subclass of an outer class? A. Static class FooBar{} B. Private class FooBar{}

C. Abstract public class FooBar{} D. Final public class FooBar{} E. Final abstract class FooBar{} Answer: D

Question No 29 Given:

1. byte arry1, array2; 2. byte array3 ; 3. byte array4;

If each array has been initialized, which statement will cause a comp

iler error?

A. Array2 = array1; B. Array2 = array3; C. Array2 = array4; D. Both A and B E. Both A and C F. Both B and C Answer: F

Question No 30 Exhibit:

1. class super ( 2. public int I = 0; 3.

4. public super (string text) ( 5. I = 1 6. ) 7. ) 8.

9. public class sub extends super ( 10. public sub (string text) ( 11. i= 2 12. ) 13.

14. public static void main (straing args) ( 15. sub sub = new sub (“Hello”); 16. system.out. PrintIn(sub.i); 17. ) 18. )

What is the result?

A. Compilation will fail.

B. Compilation will succeed and the program will print “0” C. Compilation will succeed and the program will print “1” D. Compilation will succeed and the program will print “2” Answer: A

Question No 31 Given:

1. public class returnIt (

2. returnType methodA(byte x, double y) ( 3. return (short) x/y * 2; 4. ) 5. )

What is the valid returnType for methodA in line 2? A. Int B. Byte

C. Long D. Short E. Float F. Double Answer: F

Question No 32

Given the ActionEvent, which method allows you to identify the affected component? A. GetClass. B. GetTarget. C. GetSource. D. GetComponent.

E. GetTargetComponent. Answer: C

Question No 33

Which is a method of the MouseMotionListener interface? A. Public void mouseMoved(MouseEvent) B. Public boolean mouseMoved(MouseEvent) C. Public void mouseMoved(MouseMotionEvent) D. Public boolean MouseMoved(MouseMotionEvent) E. Public boolean mouseMoved(MouseMotionEvent) Answer: A

Question No 34 Exhibit:

1. import java.awt*; 2.

3. public class X extends Frame (

4. public static void main(string args) ( 5. X x = new X (); 6. X.pack();

7. x.setVisible(true); 8. ) 9.

10. public X () (

11. setlayout (new GridLayout (2,2)); 12.

13. Panel p1 = new panel(); 14. Add(p1);

15. Button b1= new Button (“One”); 16. P1.add(b1); 17.

18. Panel p2 = new panel(); 19. Add(p2);

20. Button b2= new Button (“Two”);

21. P2.add(b2); 22.

23. Button b3= new Button (“Three”); 24. add(b3); 25.

26. Button b4= new Button (“Four”); 27. add(b4); 28. ) 29. )

Which two statements are true? (Choose Two)

A. All the buttons change height if the frame height is resized. B. All the buttons change width if the Frame width is resized.

C. The size of the button labeled “One” is constant even if the Frame is resized.

D. Both width and height of the button labeled “Three” might change if the Frame is resized. Answer: C, D ||| Question No 35

You are assigned the task of building a panel containing a TextArea at the top, a label directly below it,

and a button directly below the label. If the three components are added directly to the panel. Which

layout manager can the panel use to ensure that the TextArea absorbs all of the free vertical space when the panel is resized? A. GridLayout. B. CardLayout. C. FlowLayout. D. BorderLayout. E. GridBagLayout. Answer: E

Question No 36

Which gets the name of the parent directory file “file.txt”? A. String name= File.getParentName(“file.txt”); B. String name= (new File(“file.txt”)).getParent();

C. String name = (new File(“file.txt”)).getParentName(); D. String name= (new File(“file.txt”)).getParentFile(); E. Directory dir=(new File (“file.txt”)).getParentDir(); String name= dir.getName(); Answer: B

Question No 37

Which can be used to encode charS for output? A. Java.io.OutputStream.

B. Java.io.OutputStreamWriter.

7. throw new Exception (); 8. }

9. output += “1”; 10. )

11. catch(Exception e) { 12. output += “2”; 13. return; 14. )

15. finally (

16. output += “3”; 17. )

18. output += “4”; 19. ) 20.

21. public static void main (string args) ( 22. foo(0); 23. foo(1); 24. 25. ) 26. )

What is the value of the variable output at line 24? Answer: 13423 Question No 53 Given:

1. public class Foo implements Runnable ( 2. public void run (Thread t) {

3. system.out.printIn(“Running.”); 4. }

5. public static void main (String args) { 6. new thread (new Foo()).start(); 7. ) 8. )

What is the result?

A. An exception is thrown.

B. The program exists without printing anything. C. An error at line 1 causes compilation to fail. D. An error at line 2 causes the compilation to fail. E. “Running” is printed and the program exits. Answer: D

Question No 54

Which statement is true?

A. If only one thread is blocked in the wait method of an object, and another thread executes the

modify on that same object, then the first thread immediately resumes

execution.

B. If a thread is blocked in the wait method of an object, and another thread executes the notify

method on the same object, it is still possible that the first thread might never resume execution.

C. If a thread is blocked in the wait method of an object, and another thread executes the notify

method on the same object, then the first thread definitely resumes execution as a direct and sole consequence of the notify call.

D. If two threads are blocked in the wait method of one object, and another thread executes the notify

method on the same object, then the first thread that executed the wait call first definitely resumes

execution as a direct and sole consequence of the notify call. Answer: B

Question No 55

Which two CANNOT directly cause a thread to stop executing? (Choose Two)

A. Calling the yield method.

B. Calling the wait method on an object. C. Calling the notify method on an object. D. Calling the notifyAll method on an object.

E. Calling the start method on another Thread object. Answer: C, D Question No 56

Which two can be used to create a new Thread? (Choose Two) A. Extend java.lang.Thread and override the run method. B. Extend java.lang.Runnable and override the start method. C. Implement java.lang.thread and implement the run method. D. Implement java.lang.Runnable and implement the run method. E. Implement java.lang.Thread and implement the start method. Answer: A, D |||

Question No 54

Which statement is true?

A. If only one thread is blocked in the wait method of an object, and another thread executes the

modify on that same object, then the first thread immediately resumes execution.

B. If a thread is blocked in the wait method of an object, and another thread executes the notify

method on the same object, it is still possible that the first thread might never resume execution.

C. If a thread is blocked in the wait method of an object, and another thread executes the notify

method on the same object, then the first thread definitely resumes execution as a direct and sole consequence of the notify call.

D. If two threads are blocked in the wait method of one object, and another thread executes the notify

method on the same object, then the first thread that executed the wait call first definitely resumes

execution as a direct and sole consequence of the notify call. Answer: B

Question No 55

Which two CANNOT directly cause a thread to stop executing? (Choose Two)

A. Calling the yield method.

B. Calling the wait method on an object. C. Calling the notify method on an object. D. Calling the notifyAll method on an object.

E. Calling the start method on another Thread object. Answer: C, D Question No 56

Which two can be used to create a new Thread? (Choose Two) A. Extend java.lang.Thread and override the run method. B. Extend java.lang.Runnable and override the start method. C. Implement java.lang.thread and implement the run method. D. Implement java.lang.Runnable and implement the run method. E. Implement java.lang.Thread and implement the start method. Answer: A, D

Question No 57 Given:

1. public class SyncTest ( 2. private int x; 3. private int y;

4. private synchronized void setX (int i) (x=1;) 5. private synchronized void setY (int i) (y=1;) 6. public void setXY(int 1)(set X(i); setY(i);)

7. public synchronized Boolean check() (return x !=y;) 8. )

Under which conditions will check () return true when called from a different class?

A. Check() can never return true.

B. Check() can return true when setXY is called by multiple threads. C. Check() can return true when multiple threads call setX and setY s

eparately.

D. Check() can only return true if SyncTest is changed to allow x and y to be set separately. Answer: B

Question No 58 Exhibit:

1. class A implements runable ( 2. int i;

3. public void run () ( 4. try (

5. thread.sleep(5000); 6. i= 10;

7. ) catch(InterruptedException e) {} 8. ) 9. ) 10.

11. public class Test {

12. public static void main (string args) ( 13. try (

14. A a = new A ();

15. Thread t = new Thread (a); 16. t.start(); 17.

18. int j= a.i; 19.

20. ) catch (Exception e) {} 21. ) 22. )

Which statement al line 17 will ensure that j=10 at line 19? A. a.wait(); B. t.wait(); C. t.join(); D. t.yield(); E. t.notify(); F. a.notify(); G. t.interrupt(); Answer: C

Question No 59 Exhibit:

1. public class X implements Runnable ( 2. private int x; 3. private int y; 4.

5. public static void main(String args) (

6. X that = new X();

7. (new Thread(that)) . start( ); 8. (new Thread(that)) . start( ); 9. ) 10.

11. public synchronized void run( ) ( 12. for (;;) ( 13. x++; 14. y++;

15. System.out.printIn(“x = “ + x + “, y = “ + y); 16. ) 17. ) 18. )

What is the result?

A. An error at line 11 causes compilation to fail. B. Errors at lines 7 and 8 cause compilation to fail.

C. The program prints pairs of values for x and y that might not always be the same on the same line (for example, “x=2, y=1”)

D. The program prints pairs of values for x and y that are always the same on the same line (for

example, “x=1, y=1”. In addition, each value appears twice (for example, “x=1, y=1” followed by “x=1, y=1”)

E. The program prints pairs of values for x and y that are always the same on the same line (for

example, “x=1, y=1”. In addition, each value appears twice (for example, “x=1, y=1” followed by “x=2s, y=2”) Answer: E

QUESTION NO: 60

Which two CANNOT directly cause a thread to stop executing? (Choose Two)

A. Existing from a synchronized block. B. Calling the wait method on an object. C. Calling notify method on an object.

D. Calling read method on an InputStream object.

E. Calling the SetPriority method on a Thread object. Answer: A, C ||| QUESTION NO: 61 Exhibit

1. public class SyncTest{

2. public static void main(String args) { 3. final StringBuffer s1= new StringBuffer();

A. An inner class may be declared as static.

B. An anonymous inner class can be declared as public. C. An anonymous inner class can be declared as private. D. An anonymous inner class can extend an abstract class. E. An anonymous inner class can be declared as protected. Answer: A, D QUESTION NO: 74 Exhibit:

1. public class Mycircle { 2. public double radius; 3. public double diameter; 4.

5. public void setRadius(double radius) 6. this.radius = radius;

7. this.diameter= radius * 2; 8. } 9.

10. public double getRadius() { 11. return radius; 12. } 13. }

Which statement is true?

A. The Mycircle class is fully encapsulated.

B. The diameter of a given MyCircle is guaranteed to be twice its radius.

C. Lines 6 and 7 should be in a synchronized block to ensure encapsulation.

D. The radius of a MyCircle object can be set without affecting its diameter. Answer: B

QUESTION NO: 75

You want to limit access to a method of a public class to members of the same class. Which access

modifier accomplishes this objective? A. Public B. Private C. Protected D. Transient

E. No access modifier is required Answer: B

QUESTION NO: 76 Exhibit:

ClassOne.java

1. package com.abc.pkg1;

2. public class ClassOne { 3. private char var = ‘a‘; 4. char getVar() {return var;} 5. }

ClassTest.java

1. package com.abc.pkg2;

2. import com.abc.pkg1.ClassOne;

3. public class ClassTest extends ClassOne { 4. public static void main(Stringargs) { 5. char a = new ClassOne().getVar(); 6. char b = new ClassTest().getVar(); 7. } 8. }

What is the result?

A. Compilation will fail.

B. Compilation succeeds and no exceptions are thrown.

C. Compilation succeeds but an exception is thrown at line 5 in ClassTest.java.

D. Compilation succeeds but an exception is thrown at line 6 in ClassTest.java. Answer: B

QUESTION NO: 77 Given:

1. public class ArrayTest {

2. public static void main (Stringargs) { 3. float f1, f2;

4. f1 = new float [10]; 5. f2 = f1;

6. System.out.printIn (“f2[0]=” + f2[0]); 7. } 8. }

What is the result?

A. It prints f2[0] = 0.0 B. It prints f2[0] = NaN

C. An error at line 5 causes compile to fail. D. An error at line 6 causes compile to fail.

E. An error at line 6 causes an exception at runtime. Answer: A ||| QUESTION NO: 78

Which two statements are true regarding the creation of a default constructor? (Choose Two)

A. The default constructor initializes method variables.

B. The compiler always creates a default constructor for every class.

C. The default constructor invokes the no-parameter constructor of the superclass.

D. The default constructor initializes the instance variables declared in the class.

E. When a class has only constructors with parameters, the compiler does not create a default constructor. Answer: D, E QUESTION NO: 79 Exhibit:

1. class super {

2. public int getLength() {return 4;} 3. } 4.

5. public class Sub extends Super { 6. public long getLength() {return 5;} 7.

8. public static void main (Stringargs) { 9. super sooper = new Super (); 10. Sub sub = new Sub(); 11. System.out.printIn(

12. sooper.getLength()+ “,” + sub.getLength() }; 13. } 14. }

What is the output? A. 4, 4 B. 4, 5 C. 5, 4 D. 5, 5

E. The code will not compile. Answer: E

QUESTION NO: 80 Given:

1. public abstract class Test { 2. public abstract void methodA(); 3.

4. public abstract void methodB() 5. {

6. System.out.printIn(“Hello”); 7. } 8. }

Which three changes (made independently) allow the code to compile? (Choose Three)

A. Add a method body to methodA.

B. Replace lines 5-7 with a semicolon (“.”)

C. Remove the abstract qualifier from the declaration of Test. D. Remove the abstract qualifier from the declaration of methodB. E. Remove the abstract qualifier from the declaration of methodA. F. Remove methodB in its entirely and change class o interface in line 1.

Answer: B, D, F

QUESTION NO: 81

Which determines if “prefs” is a directory and exists on the file system?

A. Boolean exists=Directory.exists (“prefs”); B. Boolean exists=(new File(“prefs”)).isDir();

C. Boolean exists=(new Directory(“prefs”)).exists(); D. Boolean exists=(new File(“prefs”)).isDirectory(); E. Boolean exists=true; Try{

Directory d = new Directory(“prefs”); }

catch (FileNotFoundException e) { exists = false; }

Answer: D

QUESTION NO: 82

Which two create an InputStream and open file the “file.txt” for reading? (Choose Two)

A. InputStream in=new FileReader(“file.txt”);

B. InputStream in=new FileInputStream(“file.txt”);

C. InputStream in=new InputStreamFileReader (“file.txt”, “read”); D. FileInputStream in=new FileReader(new File(“file.txt”));

E. FileInputStream in=new FileInputStream(new File(“file.txt”)); Answer: B, E QUESTION NO 83

Which two construct an OutputSream that appends to the file “file.txt”? (Choose Two)

A. OutputStream out=new FileOutputStream(“file.txt”);

B. OutputStream out=new FileOutputStream(“file.txt”, “append”); C. FileOutputStream out=new FileOutputStream(“file.txt”, true); D. FileOutputStream out=new FileOutputStream(new file(“file.txt”)); E. OutputStream out=new FileOutputStream(new File(“file.txt”)true); Answer: C, E

QUESTION NO: 84

Which constructs a BufferedIputStream?

A. New BufferedInputStream(“in.txt”);

B. New BufferedInputStream(new File(“in.txt”)); C. New BufferedInputStream(new Writer(“in.txt”)); D. New BufferedInputStream(new Writer(“in.txt”));

E. New BufferedInputStream(new InputStream(“in.txt”)); F. New BufferedInputStream(new FileInputStream(“in.txt”)); Answer: F

QUESTION NO: 85

Which is a valid identifier? A. false B. default C. _object D. a-class Answer: C

QUESTION NO: 86 Exhibit:

1. package foo; 2.

3. import java.util.Vector; 4.

5. private class MyVector extends Vector { 6. int i = 1;

7. public MyVector() { 8. i = 2; 9. } 10. } 11.

12. public class MyNewVector extends MyVector { 13. public MyNewVector () { 14. i = 4; 15. }

16. public static void main (String args ) { 17. MyVector v = new MyNewVector(); 18. } 19. }

The file MyNewVector.java is shown in the exhibit. What is the result?

A. Compilation will succeed.

B. Compilation will fail at line 5. C. Compilation will fail at line 6. D. Compilation will fail at line 14. E. Compilation will fail at line 17. Answer: B ||| QUESTION NO: 87

Given:

1. public class Test {

2. public static void main (Stringargs) { 3. String foo = args[1]; 4. String bar = args; 5. String baz = args;

6. System.out.printIn(“baz = ” + baz); 7. } 8. }

And the output: Baz = 2

Which command line invocation will produce the output? A. Java Test 2222 B. Java Test 1 2 3 4 C. Java Test 4 2 4 2 D. Java Test 4 3 2 1 Answer: C

QUESTION NO: 88 Given:

8. int index = 1;

9. String test = new String; 10. String foo = test[index]; What is the result?

E. Foo has the value “” B. Foo has the value null C. An exception is thrown D. The code will not compile Answer: B

QUESTION NO: 89 Given:

1. public interface Foo{ 2. int k = 4; 3. }

Which three are equivalent to line 2? (Choose Three) A. Final int k = 4; B. Public int k = 4; C. Static int k = 4; D. Private int k = 4; E. Abstract int k = 4; F. Volatile int k = 4; G. Transient int k = 4; H. Protected int k = 4; Answer: A, B, C

QUESTION NO: 90 Given: 310-025

Leading the way in IT testing and certification tools, www.testking.com

- 48 -

1. public class foo { 2. static String s;

3. public static void main (Stringargs) { 4. system.out.printIn (“s=” + s); 5. } 6. }

What is the result?

A. The code compiles and “s=” is printed.

B. The code compiles and “s=null” is printed.

C. The code does not compile because string s is not initialized. D. The code does not compile because string s cannot be referenced. E. The code compiles, but a NullPointerException is thrown when toString is called. Answer: B

QUESTION NO: 91

Which two valid declarations of a char? (Choose Two) A. Char ch = “a”; B. Char ch = ‘“‘ ‘; C. Char ch = ‘cafe‘; D. Char ch = “cafe”; E. Char ch = ‘“ucafe‘; F. Char ch = ‘“u10100‘; G. Char ch = (char) true; Answer: B, E

310-025

Leading the way in IT testing and certification tools, QUESTION NO: 92 Given:

1. String foo = “blue”;

2. Booleanbar = new Boolean [1]; 3. if (bar[0]) { 4. foo = “green”; 5. }

What is the result?

A. Foo has the value of “” B. Foo has the value of null. C. Foo has the value of “blue”

D. Foo has the value of “green” E. An exception is thrown. F. The code will not compile. Answer: F

QUESTION NO: 93 Exhibit:

1. public class X {

2. public static void main (Stringargs) { 3. String s1 = new String (“true”); 4. Boolean b1 = new Boolean (true); 5. if (s2.equals(b1)) {

6. System.out.printIn(“Equal”); 7. } 8. } 9. }

What is the result?

A. The program runs and prints nothing. B. The program runs and prints “Equal”

C. An error at line 5 causes compilation to fail. D. The program runs but aborts with an exception. Answer: A

QUESTION NO: 94 Given:

1. public class Foo {

2. public static void main (String args) { 3. int i = 1; 4. int j = i++;

5. if ((i>++j) && (i++ ==j)) { 6. i +=j; 7. } 8. } 9. }

What is the final value of i? A. 1 B. 2 C. 3 D. 4 E. 5

Answer: B

QUESTION NO: 95 Exhibit:

1. public class X {

2. public static void main (Stringargs) { 3. string s = new string (“Hello”);

4. modify(s);

5. System.out.printIn(s); 6. } 7.

8. public static void modify (String s) { 9. s += “world!”; 10. } 11. }

What is the result?

E. The program runs and prints “Hello” F. An error causes compilation to fail.

G. The program runs and prints “Hello world!” H. The program runs but aborts with an exception. Answer: A

QUESTION NO: 96

Which two are equivalent? (Choose Two) A. 16>4 B. 16/2 C. 16*4 D. 16>>2 E. 16/2^2 F. 16>>>2 Answer: D, F QUESTION NO: 97 Exhibit:

1. public class X {

2. public static void main (Stringargs) { 3. int a = new int [1] 4. modify(a);

5. System.out.printIn(a[0]); 6. } 7.

8. public static void modify (int a) { 9. a[0] ++; 10. } 11. }

What is the result?

A. The program runs and prints “0” B. The program runs and prints “1”

C. The program runs but aborts with an exception.

D. An error “possible undefined variable” at line 4 causes compilation to fail.

E. An error “possible undefined variable” at line 9 causes compilat

ion to fail. Answer: B |||

QUESTION NO: 98 Given:

13. public class Foo {

14. public static void main (String args) { 15. StringBuffer a = new StringBuffer (“A”); 16. StringBuffer b = new StringBuffer (“B”); 17. operate (a,b);

18. system.out.printIn{a + “,” +b}; 19. )

20. static void operate (StringBuffer x, StringBuffer y) { 21. y.append {x}; 22. y = x; 23. ) 24. }

What is the result?

A. The code compiles and prints “A,B”. B. The code compiles and prints “A, BA”. C. The code compiles and prints “AB, B”. D. The code compiles and prints “AB, AB”. E. The code compiles and prints “BA, BA”.

F. The code does not compile because “+” cannot be overloaded for stringBuffer. Answer: B

QUESTION NO: 99 Given:

1. public class X {

2. public static void main (String args) { 3. byte b = 127; 4. byte c = 126; 5. byte d = b + c; 6. } 7. }

Which statement is true?

A. Compilation succeeds and d takes the value 253. B. Line 5 contains an error that prevents compilation. C. Line 5 throws an exception indicating “Out of range” D. Line 3 and 4 contain error that prevent compilation. E. The compilation succeeds and d takes the value of 1. Answer: B

QUESTION NO: 100 Given:

1. public class WhileFoo {

2. public static void main (String args) { 3. int x= 1, y = 6; 4. while (y--) {x--;}

5. system.out.printIn(“x=” + x “y =” + y); 6. } 7. }

What is the result?

A. The output is x = 6 y = 0 B. The output is x = 7 y = 0 C. The output is x = 6 y = -1 D. The output is x = 7 y = -1 E. Compilation will fail. Answer: E

QUESTION NO: 101

Which statement is true?

A. The Error class is a untimeException. B. No exceptions are subclasses of Error.

C. Any statement that may throw an Error must be enclosed in a try block.

D. Any statement that may throw an Exception must be enclosed in a try block.

E. Any statement that may thro a runtimeException must be enclosed in a try block. Answer: D

QUESTION NO: 102 Exhibit:

1. int I=1, j=0 2.

3. switch(i) { 4. case 2: 5. j+=6; 6.

7. case 4: 8. j+=1; 9.

10. default: 11. j +=2; 12.

13. case 0: 14. j +=4; 15. } 16.

What is the value of j at line 16?

A. 0 B. 1 C. 2 D. 4 E. 6

Answer: AE ||| QUESTION NO: 103 Given:

1. switch (i) { 2. default:

3. System.out.printIn(“Hello”); 4. )

What is the acceptable type for the variable i? A. Byte B. Long C. Float D. Double E. Object F. A and B G. C and D Answer: A

QUESTION NO: 104

You need to store elements in a collection that guarantees that no duplicates are stored. Which two

interfaces provide that capability? (Choose Two) A. Java.util.Map B. Java.util.Set C. Java.util.List

D. Java.util.StoredSet E. Java.util.StoredMap F. Java.util.Collection Answer: B, D QUESTION NO: 105

Which statement is true for the class java.util.ArrayList? A. The elements in the collection are ordered. B. The collection is guaranteed to be immutable.

C. The elements in the collection are guaranteed to be unique.

D. The elements in the collection are accessed using a unique key. E. The elements in the collections are guaranteed to be synchronized.

Answer: A

QUESTION NO: 106 Exhibit:

1. public class X implements Runnable(

2. private int x; 3. private int y; 4.

5. public static void main(Stringargs) 6. X that = new X();

7. (new Thread(that)).start(); 8. (new Thread(that)).start(); 9. ) 10.

11. public void run() ( 12. for (;;) ( 13. x++; 14. y++;

15. System.out.printIn(“x=” + x + “, y = ” + y); 16. ) 17. ) 18. )

What is the result?

A. Errors at lines 7 and 8 cause compilation to fail.

B. The program prints pairs of values for x and y that might not always be the same on the same line (for example, “x=2, y=1”).

C. The program prints pairs of values for x and y that are always the same on the same line (for

example, “x=1, y=1”. In addition, each value appears twice (for example, “x=1, y=1” followed by “x=1, y=1”).

D. The program prints pairs of values for x and y that are always the same on the same line (for

example, “x=1, y=1”. In addition, each value appears only for once (for example, “x=1, y=1” followed by “x=2, y=2”). Answer: D

QUESTION NO: 107 Given:

1. public class SyncTest { 2. private int x; 3. private int y;

4. public synchronized void setX (int i) (x=1;) 5. public synchronized void setY (int i) (y=1;)

6. public synchronized void setXY(int 1)(set X(i); setY(i);) 7. public synchronized Boolean check() (return x !=y;) 8. )

Under which conditions will check () return true when called from a d

ifferent class?

A. Check() can never return true.

B. Check() can return true when setXY is called by multiple threads. C. Check() can return true when multiple threads call setX and setY separately.

D. Check() can only return true if SyncTest is changed to allow x and y to be set separately. Answer: A

QUESTION NO: 108

Which is a method of the MouseMotionListener interface? A. Public void mouseDragged(MouseEvent) B. Public boolean mouseDragged(MouseEvent) C. Public void mouseDragged(MouseMotionEvent) D. Public boolean MouseDragged(MouseMotionEvent) E. Public boolean mouseDragged(MouseMotionEvent) Answer: A ||| QUESTION NO: 109 Given:

1. String foo = “base”; 2. foo.substring(0,3); 3. foo.concat(“ket”); 4. foo += “ball”; 5.

Type the value of foo at line 8. Answer: BASEBALL QUESTION NO 110 Given:

1. public class Test {

2. public static void leftshift(int i, int j) { 3. i<<=j; 4. }

5. public static void main(String args) { 6. int i = 4, j = 2; 7. leftshift(i, j);

8. System.out.printIn(i); 9. } 10. }

What is the result? A. 2 B. 4 C. 8 D. 16

E. The code will not compile. Answer: B

QUESTION NO 111 Given:

1. public class Foo { 2. private int val;

3. public foo(int v) (val = v;) }

4. public static void main (String args) { 5. Foo a = new Foo (10); 6. Foo b = new Foo (10); 7. Foo c = a; 8. int d = 10;

9. double e = 10.0; 10. } 11. }

Which three logical expression evaluate to true? (Choose Three) A. (a ==c) B. (d ==e) C. (b ==d) D. (a ==b) E. (b ==c) F. (d ==10.0) Answer: A, B, F QUESTION NO 112 Exhibit:

1. public class X {

2. private static int a; 3.

5. public static void main (String args) { 6. modify (a); 7. } 8.

9. public static void modify (int a) { 10. a++; 11. } 12. }

What is the result?

A. The program runs and prints “0” B. The program runs and prints “1”

C. The program runs but aborts with an exception.

D. En error “possible undefined variable” at line 5 causes compilation to fail.

F. En error “possible undefined variable” at line 10 causes compilation to fail. Answer: A

QUESTION NO 113

Exhibit:

1. public class Test {

2. public static void replaceJ(string text) { 3. text.replace (‘j‘, ‘l‘); 4. } 5.

6. public static void main(String args) { 7. string text = new String (“java”) 8. replaceJ(text);

9. system.out.printIn(text); 10. } 11. }

What is the result?

A. The program prints “lava” B. The program prints “java”

C. An error at line 7 causes compilation to fail.

D. Compilation succeeds but the program throws an exception. Answer: B

QUESTION NO 114

Which two are equivalent? (Choose Two) A. 3/2 B. 3<2 C. 3*4 D. 3<<2 E. 3*2^2 F. 3<<<2

Answer: C, D QUESTION NO 115

What is the numerical range of a char? A. 0 . . . 32767 B. 0 . . . 65535 C. –256 . . . 255 D. –32768 . . . 32767

E. Range is platform dependent. Answer: B ||| QUESTION NO 116 Given:

1. public class Test {

2. public static void main (String args) { 3. unsigned byte b = 0; 4. b--; 5. 6. } 7. }

What is the value of b at line 5? A. -1 B. 255 C. 127

D. Compilation will fail.

E. Compilation will succeed but the program will throw an exception at line 4. Answer: D

QUESTION NO 117 Given:

1. public class Foo {

2. public void main (String args) {

3. system.out.printIn(“Hello World.”); 4. } 5. }

What is the result?

A. An exception is thrown. B. The code does no compile.

C. “Hello World.” Is printed to the terminal. D. The program exits without printing anything. Answer: A

QUESTION NO 118 Given:

1. //point X

2. public class foo (

3. public static void main (Stringargs) throws Exception { 4. java.io.printWriter out = new java.io.PrintWriter ( 5. new java.io.outputStreamWriter (System.out), true; 6. out.printIn(“Hello”); 7. } 8. }

Which statement at PointX on line 1 allows this code to compile and run?

A. Import java.io.*; B. Include java.io.*;

C. Import java.io.PrintWriter; D. Include java.io.PrintWriter; E. No statement is needed. Answer: E

QUESTION NO 119

Which will declare a method that is available to all members of the same package and can be referenced without an instance of the class? A. Abstract public void methoda();

B. Public abstract double methoda(); C. Static void methoda(double d1){} D. Public native double methoda() {} E. Protected void methoda(double d1) {} Answer: C

QUESTION NO 120

Which type of event indicates a key pressed on a java.awt.Component? A. KeyEvent

B. KeyDownEvent C. KeyPressEvent D. KeyTypedEvent E. KeyPressedEvent Answer: A

QUESTION NO 121 Exhibit:

1. import java.awt.*; 2.

3. public class X extends Frame {

4. public static void main (String args) { 5. X x = new X(); 6. x.pack();

7. x.setVisible(true); 8. } 9.

10. public X() {

11. setLayout (new BordrLayout()); 12. Panel p = new Panel ();

13. add(p, BorderLayout.NORTH);

14. Button b = new Button (“North”); 15. p.add(b):

16. Button b = new Button (“South”); 17. add(b1, BorderLayout.SOUTH): 18. } 19. }

Which two statements are true? (Choose Two)

A. The buttons labeled “North” and “South” will have the same width.

B. The buttons labeled “North” and “South” will have the same height.

C. The height of the button labeled “North” can very if the Frame is resized.

D. The height of the button labeled “South” can very if the Frame is resized.

E. The width of the button labeled “North” is constant even if the

Frame is resized.

F. The width of the button labeled “South” is constant even if the Frame is resized. Answer: B, E QUESTION NO 122

How can you create a listener class that receives events when the mouse is moved?

A. By extending MouseListener. B. By implementing MouseListener. C. By extending MouseMotionListener. D. By implementing MouseMotionListener.

E. Either by extending MouseMotionListener or extending MouseListener.

F. Either by implementing MouseMotion Listener or implementing MouseListener.

Answer: D ||| QUESTION NO 123

Which statement is true?

A. A grid bag layout can position components such that they span multiple rows and/or columns.

B. The “North” region of a border layout is the proper place to locate a menuBar component in a Frame.

C. Components in a grid bag layout may either resize with their cell, or remain centered in that cell at their preferred size.

D. A border layout can be used to position a component that should maintain a constant size even when the container is resized. Answer: A

QUESTION NO 124

You want a class to have access to members of another class in the same package. Which is the most

restrictive access modifier that will accomplish that will accomplish this objective? A. Public B. Private C. Protected D. Transient

E. No access modifier is required. Answer: E

QUESTION NO 125

Which two statements are true regarding the creation of a default constructor? (Choose Two)

A. The default constructor initializes method variables.

B. The default constructor invokes the no-parameter constructor of the superclass.

C. The default constructor initializes the instance variables declared in the class.

D. If a class lacks a no-parameter constructor,, but has other constructors, the compiler creates a default constructor.

E. The compiler creates a default constructor only when there are no other constructors for the class. Answer: C, E QUESTION NO 126 Given:

1. public class OuterClass { 2. private double d1 1.0; 3. //insert code here 4. }

You need to insert an inner class declaration at line2. Which two inner class declarations are valid? (Choose Two)

A. static class InnerOne {

public double methoda() {return d1;} }

B. static class InnerOne {

static double methoda() {return d1;} }

C. private class InnerOne {

public double methoda() {return d1;} }

D. protected class InnerOne {

static double methoda() {return d1;} }

E. public abstract class InnerOne { public abstract double methoda(); }

Answer: C, E

QUESTION NO 127

Which two declarations prevent the overriding of a method? (Choose Two)

A. Final void methoda() {} B. Void final methoda() {} C. Static void methoda() {}

D. Static final void methoda() {}

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