SCJP考试题310-025(第二套<2>)19-50/147

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 compiler 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.
C. Java.io.EncodeOutputStream.
D. Java.io.EncodeWriter.
E. Java.io.BufferedOutputStream.
Answer: B

Question No 38
The file “file.txt” exists on the file system and contsins ASCII text.
Given:
38. try {
39. File f = new File(“file.txt”);
40. OutputStream out = new FileOutputStream(f, true);
41. }
42. catch (IOException) {}
What is the result?
A. The code does not compile.
B. The code runs and no change is made to the file.
C. The code runs and sets the length of the file to 0.
D. An exception is thrown because the file is not closed.
E. The code runs and deletes the file from the file system.
Answer: A
Question No 39
Which constructs a DataOutputStream?
A. New dataOutputStream(“out.txt”);
B. New dataOutputStream(new file(“out.txt”));
C. New dataOutputStream(new writer(“out.txt”));
D. New dataOutputStream(new FileWriter(“out.txt”));
E. New dataOutputStream(new OutputStream(“out.txt”));
F. New dataOutputStream(new FileOutputStream(“out.txt”));
Answer: F
Question No 40
What writes the text “ ” to the end of the file “file.txt”?
A. OutputStream out= new FileOutputStream (“file.txt”);
Out.writeBytes (“ /n”);
B. OutputStream os= new FileOutputStream (“file.txt”, true);
DataOutputStream out = new DataOutputStream(os);
out.writeBytes (“ /n”);
C. OutputStream os= new FileOutputS

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