mockcert03.txt

一道ＪＡＶＡ方面的试题 很不错的 我很喜欢

Question 1
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Which of the following lines will compile without warning or error.

Mutiple: 
1) float f = 1.3;
2) char c = "a";
3) byte b = 257;
4) boolean b = null;
5) int i = 10;


Question 2
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What will happen if you try to compile and run the following code

public class MyClass {
  public static void main(String arguments[]){
    amethod(arguments);
  }
  public void amethod(String[] arguments){
    System.out.println(arguments);
    System.out.println(arguments[1]);
  }
}

Mutiple: 
1) error Can't make static reference to void amethod.
2) error method main not correct
3) error array must include parameter
4) amethod must be declared with String


Question 3
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Which of the following will compile without error

Mutiple: 
1) import java.awt.*;
package Mypackage;
class Myclass {}
2) package MyPackage;
import java.awt.*;
class MyClass{}
3) /*This is a comment */
package MyPackage;
import java.awt.*;
class MyClass{}


Question 4
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A byte can be of what size

Mutiple: 
1) -128 to 127
2) (-2 power 8 )-1 to 2 power 8
3) -255 to 256
4) depends on the Java Virtual machine


Question 5
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What will be printed out if this code is run with the following command line
java myprog good morning

public class myprog{
  public static void main(String argv[]){
    System.out.println(argv[2])
  }
}

Mutiple: 
1) myprog
2) good
3) morning
4) Exception raised: "java.lang.ArrayIndexOutOfBoundsException: 2"


Question 6
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Which of the following are legal identifiers

Mutiple: 
1) 2variable
2) variable2
3) _whatavariable
4) _3_
5) $anothervar


Question 7
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Which of the following are java reserved words

Mutiple: 
1) if
2) then
3) goto
4) while
5) case


Question 8
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What will happen when you compile the following code

public class MyClass{
  static int i; 
  public static void main(String argv[]){
    System.out.println(i);
  }
}

Only One: 
1) Error Variable i may not have been initialized
2) null
3) 1
4) 0


Question 9
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What will happen if you try to compile and run the following code

public class Q {
  public static void main(String argv[]){
    int anar[]= new int[]{1,2,3};

    System.out.println(anar[1]);//此题答案有错，应当是3）
  }
}

Mutiple: 
1) 1
2) Error anar is referenced before it is initialized
3) 2
4) Error size of array must be defined


Question 10
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What will happen if you try to compile and run the following code

public class Q {
  public static void main(String argv[]){
    int anar[]= new int[5];

    System.out.println(anar[0]);
  }
}

Mutiple: 
1) Error: anar is referenced before it is initialized
2) null
3) 0
4) 5


Question 11
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What will be the result of attempting to compile and run the following code

abstract class MineBase {
  abstract void amethod(); 
  static int i;
}

public class Mine extends MineBase{
  public static void main(String argv[]){
    int[] ar = new int[5];
    for(i = 0;i < ar.length;i++)
       System.out.println(ar[i]);
    }
}

Mutiple: 
1) a sequence of 5 0's will be printed
2) Error: ar is used before it is initialized
3) Error Mine must be declared abstract
4) IndexOutOfBoundes Error i


Question 12
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What will be printed out if you attempt to compile and run the following code

int i = 1;
switch (i) {
  case 0:
         System.out.println("zero");
         break;
  case 1:
         System.out.println("one");
  case 2:
         System.out.println("two");
  default:
         System.out.println("default");
}

Mutiple: 
1) one
2) one, default
3) one, two, default
4) default


Question 13
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What will be printed out if you attempt to compile and run the following code

int i = 9;
switch (i) {
       default:
              System.out.println("default");
       case 0:
              System.out.println("zero");
              break;
       case 1:
              System.out.println("one");
       case 2:
              System.out.println("two");
}

Mutiple: 
1) default
2) default, zero
3) error default clause not defined
4) no output displayed


Question 14
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Which of the following lines of code will compile without error

Mutiple: 
1) int i=0;
if(i){
      System.out.println("Hello");
}
2) boolean b = true;
boolean b2 = true;
if(b==b2){
   System.out.println("So true");
}
3) int i=1;
int j = 2;
if(i ==1|| j==2)
System.out.println("OK");
4) int i=1;
int j = 2;
if(i ==1 &| j==2)
System.out.println("OK");


Question 15
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What will be output if you try to compile and run the following code and and there is 
no file called Hello.txt in the current directory.

import java.io.*;
public class Mine{
  public static void main(String argv[]){

      Mine m = new Mine();
      System.out.println(m.amethod());
  }

  public int amethod(){
      try {
           FileInputStream dis = new FileInputStream("Hello.txt");
      }catch (FileNotFoundException fne) {
           System.out.println("No such file found");
           return -1;
      }catch(IOException ioe) {
      }finally{
           System.out.println("Doing finally");
      }
      return 0;
  }
}

Mutiple: 
1) No such file found
2) No such file found ,-1
3) No such file found, doing finally, -1
4) 0


Question 16
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What tags are mandatory when creating HTML to display an applet

Mutiple: 
1) name, height, width
2) code, name
3) codebase, height, width
4) code, height, width


Question 17
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What will happen if you attempt to compile and run the following code

class Base {}
class Sub extends Base {}
class Sub2 extends Base {}

public class CEx{
  public static void main(String argv[]){
    Base b = new Base();
    Sub s = (Sub) b;
  }
}

Only One: 
1) Compile and run without error
2) Compile time Exception
3) Runtime Exception


Question 18
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If the following HTML code is used to display the applet in the code MgAp what will be displayed at the console.

<applet code = MgAp.class height=400 width=400 parameter HowOld=30 > 
</applet>

import java.applet.*;
import java.awt.*;
public class MgAp extends Applet{

public void init(){
  System.out.println(getParameter("age"));
}
}

Mutiple: 
1) Error no such parameter
2) 0
3) null
4) 30


Question 19
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You are browsing the Java HTML documentation for information on the java.awt.TextField component. You want to create Listener code to respond to focus events. The only Listener method listed is addActionListener. How do you go about finding out about Listener methods.

Mutiple: 
1) Define your own Listener interface according to the event to be tracked
2) Use the search facility in the HTML documentation for the listener needed
3) Move up the hierarchy in the HTML documentation to locate methods in base 
classes
4) Subclass awt.event with the appropriate Listener method


Question 20
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What will be displayed when you attempt to compile and run the following code

//Code start
import java.awt.*;

public class Butt extends Frame{
  public static void main(String argv[]){
    Butt MyBut= new Butt(); 
  }

  Butt(){
    Button HelloBut = new Button("Hello");
    Button ByeBut = new Button("Bye");
    add(HelloBut);
    add(ByeBut);
    setSize(300,300);
    setVisible(true);
  }
}//Code end

Only One: 
1) ) Two buttons side by side occupying all of the frame, Hello on the left and Bye on 
the right
2) One button occupying the entire frame saying Hello
3) One button occupying the entire frame saying Bye
4) Two buttons at the top of the frame one saying Hello the other saying Bye


Question 21
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In the following code fragment from an applet, we know that the getParameter call may return a null if there is no parameter named size. Which logical operator should replace X in line 5 to ensure that a NullPointerException is not generated if tmp is null.

1. int sz;
2. public void init(){
3.   sz=10;
4.   String tmp=getParameter("size");
5.   if(tmp!=null X tmp.equals("BIG")) sz=20;
6. }

Mutiple: 
1) Replace X with '&'
2) Replace X with '&&'
3) Replace X with '|'
4) Replace X with '||'


Question 22
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Which of the following statements results in C containing the special "Not a Number" value?

Mutiple: 
1) float C=1234.0F/0.0F;
2) float C=(float)java.lang.Math.sqrt(-1.0);
3) float C=Float.MIN_VALUE/Float.MAX_VALUE;


Question 23
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You are writing a java class in a file named "MyClass.java", this class must be accessible by all classes in a large project. Which of the following would be correct class declarations?