JAVA认证历年真题：SCJP考试真题和解析(1)(3)

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.

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