scjp试题－scjpmockexam4.txt

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1) Error: amethod parameter does not match variable  
2) 20 and 40  
3) 10 and 40  
4) 10, and 20  

Answer to Question 41  


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Question 42) 

What code placed after the comment //For loop would populate the elements of the array ia[] with values of the variable i.?  

public class Lin{ 
public static void main(String argv[]){ 
Lin l = new Lin(); 
l.amethod(); 
} 
public void amethod(){ 
int ia[] = new int[4]; 
//Start For loop 
{ 
ia[i]=i; 
System.out.println(ia[i]); 
} 
} 
} 
1) for(int i=0; i < ia.length() -1; i++)  
2) for (int i=0; i< ia.length(); i++)  
3) for(int i=1; i < 4; i++)  
4) for(int i=0; i< ia.length;i++)  

Answer to Question 42  


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Question 43) 

What will be the result when you try to compile and run the following code?  

private class Base{ 
Base(){ 
int i = 100; 
System.out.println(i); 
} 
} 

public class Pri extends Base{ 
static int i = 200; 
public static void main(String argv[]){ 
Pri p = new Pri(); 
System.out.println(i); 
} 
} 
1) Error at compile time  
2) 200  
3) 100 followed by 200  
4) 100  

Answer to Question 43  


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Question 44) 
What will the following code print out?  

public class Oct{ 
public static void main(String argv[]){ 
Oct o = new Oct(); 
o.amethod(); 
} 
public void amethod(){ 
int oi= 012; 
System.out.println(oi); 
} 
} 
1)12  
2)012  
3)10  
4)10.0  


Answer to Question 44  


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Question 45 
What will happen when you try compiling and running this code?  

public class Ref{ 
public static void main(String argv[]){ 
Ref r = new Ref(); 
r.amethod(r); 
} 
public void amethod(Ref r){ 
int i=99; 
multi(r); 
System.out.println(i); 
} 
public void multi(Ref r){ 
r.i = r.i*2; 
} 
} 
1) Error at compile time  
2) An output of 99  
3) An output of 198  
4) An error at runtime  

Answer to Question 45  


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Question 46) 
You need to create a class that will store a unique object elements. You do not need to sort these elements but they must be unique.  

What interface might be most suitable to meet this need?  

1)Set  
2)List  
3)Map  
4)Vector  


Answer to Question 46  


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Question 47) 
Which of the following will successfully create an instance of the Vector class and add an element?  

1) Vector v=new Vector(99);  
v[1]=99;  


2) Vector v=new Vector();  
v.addElement(99);  


3) Vector v=new Vector();  
v.add(99);  


4 Vector v=new Vector(100);  
v.addElement("99");  

Answer to Question 47  


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Question 48) 
You have created a simple Frame and overridden the paint method as follows  

public void paint(Graphics g){ 
g.drawString("Dolly",50,10); 

} 

What will be the result when you attempt to compile and run the program?  

1) The string "Dolly" will be displayed at the centre of the frame  
2) An error at compilation complaining at the signature of the paint method  
3) The lower part of the word Dolly will be seen at the top of the frame, with the top hidden.  
4) The string "Dolly" will be shown at the bottom of the frame.  

Answer to Question 48  


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Question 49) 
What will be the result when you attempt to compile this program?  

public class Rand{ 
public static void main(String argv[]){ 
int iRand; 
iRand = Math.random(); 
System.out.println(iRand); 
} 
} 
1) Compile time error referring to a cast problem  
2) A random number between 1 and 10  
3) A random number between 0 and 1  
4) A compile time error about random being an unrecognised method  

Answer to Question 49  


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Question 50) 
Given the following code  

import java.io.*; 
public class Th{ 
public static void main(String argv[]){ 
Th t = new Th(); 
t.amethod(); 
} 
public void amethod(){ 
try{ 
ioCall(); 
}catch(IOException ioe){} 
} 
} 
What code would be most likely for the body of the ioCall method  

1) public void ioCall ()throws IOException{ 
DataInputStream din = new DataInputStream(System.in); 
din.readChar(); 
} 
2) public void ioCall ()throw IOException{ 
DataInputStream din = new DataInputStream(System.in); 
din.readChar(); 
} 
3) public void ioCall (){ 
DataInputStream din = new DataInputStream(System.in); 
din.readChar(); 
} 
4) public void ioCall throws IOException(){ 
DataInputStream din = new DataInputStream(System.in); 
din.readChar(); 

} 
Answer to Question 50  


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Question 51) 
What will happen when you compile and run the following code?  

public class Scope{ 
private int i; 
public static void main(String argv[]){ 
Scope s = new Scope(); 
s.amethod(); 
}//End of main 
public static void amethod(){ 
System.out.println(i); 
}//end of amethod 
}//End of class 
1) A value of 0 will be printed out  
2) Nothing will be printed out  
3) A compile time error  
4) A compile time error complaining of the scope of the variable i  

Answer to Question 51  


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Question 52) 

You want to lay out a set of buttons horizontally but with more space between the first button and the rest. You are going to use the GridBagLayout manager to control the way the buttons are set out. How will you modify the way the GridBagLayout acts in order to change the spacing around the first button?  


1) Create an instance of the GridBagConstraints class, call the weightx() method and then pass the GridBagConstraints instance with the component to the setConstraints method of the GridBagLayout class.  

2) Create an instance of the GridBagConstraints class, set the weightx field and then pass the GridBagConstraints instance with the component to the setConstraints method of the GridBagLayout class.  

3) Create an instance of the GridBagLayout class, set the weightx field and then call the setConstraints method of the GridBagLayoutClass with the component as a parameter.  

4) Create an instance of the GridBagLayout class, call the setWeightx() method and then pass the GridBagConstraints instance with the component to the setConstraints method of the GridBagLayout class.  

Answer to Question 52  


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Question 53) 

Which of the following can you perform using the File class?  

1) Change the current directory  
2) Return the name of the parent directory  
3) Delete a file  
4) Find if a file contains text or binary information  

Answer to Question 53  






Question 54) 

Which statement is true of the following code? 


public class Rpcraven{ 
public static void main(String argv[]){ 
Pmcraven pm1 = new Pmcraven("one"); 
pm1.run(); 
Pmcraven pm2 = new Pmcraven("two"); 
pm2.run(); 

} 
} 

class Pmcraven extends Thread{ 
private String sTname=""; 
Pmcraven(String s){ 
sTname = s; 

} 
public void run(){ 
for(int i =0; i < 2 ; i++){ 
try{ 
sleep(1000); 
}catch(InterruptedException e){} 

yield(); 
System.out.println(sTname); 
} 

} 
} 

1) Compile time error, class Rpcraven does not import java.lang.Thread 
2) Output of One One Two Two 
3) Output of One Two One Two 
4) Compilation but no output at runtime 


Answer to Question 54  


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Question 55) 
You are concerned that your program may attempt to use more memory than is available. To avoid this situation you want to ensure that the Java Virtual Machine will run its garbage collection just before you start a complex routine. What can you do to be certain that garbage collection will run when you want .  

1) You cannot be certain when garbage collection will run  
2) Use the Runtime.gc() method to force garbage collection  
3) Ensure that all the variables you require to be garbage collected are set to null  
4) Use the System.gc() method to force garbage collection  

Answer to Question 55  


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Question 56) 
You are using the GridBagLayout manager to place a series of buttons on a Frame. You want to make the size of one of the buttons bigger than the text it contains. Which of the following will allow you to do that?  

1) The GridBagLayout manager does not allow you to do this  
2) The setFill method of the GridBagLayout class  
3) The setFill method of the GridBagConstraints class  
4) The fill field of the GridBagConstraints class  


Answer to Question 56  


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Question 57) 
Which of the following most closely describes a bitset collection?  

1) A class that contains groups of unique sequences of bits  
2) A method for flipping individual bits in instance of a primitive type  
3) An array of boolean primitives that indicate zeros or ones  
4) A collection for storing bits as on-off information, like a vector of bits  

Answer to Question 57  


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Question 58) 

You have these files in the same directory. What will happen when you attempt to compile and run Class1.java if you have not already compiled Base.java  

//Base.java 
package Base; 
class Base{ 
protected void amethod(){ 
System.out.println("amethod"); 
}//End of amethod 
}//End of class base 
package Class1; 
//Class1.java 
public class Class1 extends Base{ 
public static void main(String argv[]){ 
Base b = new Base(); 
b.amethod(); 
}//End of main 

}//End of Class1 
1) Compile Error: Methods in Base not found  
2) Compile Error: Unable to access protected method in base class  
3) Compilation followed by the output "amethod"  
4)Compile error: Superclass Class1.Base of class Class1.Class1 not found  

Answer to Question 58  


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Question 59) 
What will happen when you attempt to compile and run the following code  

class Base{ 
private void amethod(int iBase){ 
System.out.println("Base.amethod"); 
} 
} 



class Over extends Base{ 
public static void main(String argv[]){ 
Over o = new Over(); 
int iBase=0; 
o.amethod(iBase); 
} 

public void amethod(int iOver){ 
System.out.println("Over.amethod"); 
} 
} 
1) Compile time error complaining that Base.amethod is private  
2) Runtime error complaining that Base.amethod is private  
3) Output of "Base.amethod" 
4) Output of "Over.amethod"  


Answer to Question 59  


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Question 60) 
You are creating an applet with a Frame that contains buttons. You are using the GridBagLayout manager and you have added Four buttons. At the moment the buttons appear in the centre of the frame from left to right. You want them to appear one on top of the other going down the screen. What is the most appropriate way to do this.  


1) Set the gridy value of the GridBagConstraints class to a value increasing from 1 to 4  
2) set the fill value of the GridBagConstraints class to VERTICAL  
3) Set the ipady value of the GridBagConstraints class to a value increasing from 0 to 4  
4) Set the fill value of the GridBagLayouts class to GridBag.VERTICAL  

Answer to Question 60  

If you have a copy of the Roberts and Heller Java2 Guide that says the exam does not cover the GridBagLayout, this is an error. You can confirm this by looking at the online errata at  

http://www.sybex.com/cgi-bin/rd_err_temp.pl?2463err.html  


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Answers 

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Answer 1) 
Back to question 1)  
Objective 4.5) 

5) int i=10;  

explanation:  
1) float f=1.3;  
Will not compile because the default type of a number with a floating point component is a double. This would compile with a cast as in  

float f=(float) 1.3  


2) char c="a";  

Will not compile because a char (16 bit unsigned integer) must be defined with single quotes. This would compile if it were in the form  

char c=’a’;