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详细介绍scjp考试指南包括基础语法和文件读取

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  5.     Window grid = new Frame();
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  6.     grid.setLayout(new GridLayout(0,1,2,3));
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  7.     for(int i=0;i<labels.length;i++) {
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  8.       grid.add(new Button(labels[i]));
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  9.     }
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 10.     grid.pack(); 
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 11.     grid.setVisible(true);
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 12. }
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Select the one right answer
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a. The program will not show any buttons at all.
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b. It will place all buttons in one row - A B C D E F.
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c. It will place all buttons in one column, i.e., each button in a separate row - A B C D E and F.
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d. It will place pairs of buttons in three separate row A B, C D and E F.
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Q67
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What happens when this method is called with an input of "Java rules"?	
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 1. public String addOK(String S) {
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 2.   S += " OK!";
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 3.   return S;
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 4. }
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Select one correct answer
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a. The method will return "OK!";
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b. A runtime exception will be thrown.
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c. The method will return "Java rules OK!".
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d. The method will return "Java rules".
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Q68
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What happens during execution of the following program?
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 1. public class OperandOrder {
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 2.   public static void main(String args[]) {
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 3.     int i=0;
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 4.     int a[] = {3,6};
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 5.     a[i] = i = 9;
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 6.     System.out.println(i + " " + a[0] + " " + a[1]);
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 7.   }
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 8. }
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Select one correct answer.
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a. Raises "ArrayIndexOutOfBoundsException".
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b. Prints "9 9 6".
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c. Prints "9 0 6".
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d. Prints "9 3 6".
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Q69
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Which statements about the output of the following program are true?	
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  1. public class Logic {
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  2.   public static void main(String args[]) {
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  3.     int i = 0;
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  4.     int j = 0;
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  5.     boolean t = true;
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  6.     boolean r;
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  7.     r = (t & 0<(i += 1));
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  8.     r = (t && 0<(i += 2));
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  9.     r = (t | 0<(j += 1));
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 10.     r = (t || 0<(j += 2));
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 11.     System.out.println(i + " " + j);
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 12.   }
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 13. }     
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Select all the valid answers.
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a. The first digit printed is 1.
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b. The first digit printed is 3.
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c. The second digit printed is 3.
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d. The second digit printed is 1.
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Q70
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What kind of stream is the System.out object?	
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a. java.io.BufferedWriter
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b. java.io.PrintStream
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c. java.io.FileWriter
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d. java.io.OutputStreamWriter
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Q71
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Which of the following events has a matching adapter class that implements the appropriate listener interface?	
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Select all correct answers.
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a. java.awt.event.MouseEvent
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b. java.awt.event.ActionEvent
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c. java.awt.event.FocusEvent
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d. java.awt.event.ItemEvent
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Q72
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Here is a partial listing of a class to represent a game board in a networked game. It is desired to prevent collisions due to more than one Thread using the addPic method to modify the array of Image references.	
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  1.  class Board extends Object {
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  2.    Image[] pics = new Image[64];
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  3.    int active = 0;
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  4.    public boolean addPic( Image mg, int pos) {
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  5.      synchronized (this) { 
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  6.        if (pics[pos] == null) 
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  7.          { active++ ; pics[pos] = mg; return true; }
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  8.        else
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  9.          return false;  
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 10.      }
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 11.    }
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 12.    // remainder of class 
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Select all the alternatives for line 5 that would accomplish this.
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a. synchronized (this)
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b. synchronized (pics)
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c. synchronized (mg)
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d. synchronized (active)
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Q73
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Given an object created by the following class	
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 1.   class Example extends Object {
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 2.     public void Increment (Integer N) {
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 3.       N = new Integer( N.intValue() + 1);
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 4.     }
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 6.     public void Result(int x) {
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 7.       Integer X = new Integer(x);
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 8.       Increment(X);
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 9.       System.out.println("New value is" + X);
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 10.    }
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 11.  }
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What happens when a program calls the Result method with a value of 30?
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a. The message "New value is 31" goest to the standard output.
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b. The message "New value is 29" goes to the standard output.
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c. The message "New Value is 30" goes to the standard output.
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d. The program fails to compile.
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Q74
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What is the output of the following program	
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 1.   public class Test { 
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 2.     private int i = giveMeJ(); 
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 3.     private int j = 10; 
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 4. 
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 5.     private int giveMeJ() { 
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 6.       return j;
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 7.     } 
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 8. 
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 9.     public static void main(String args[]) { 
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 10.      System.out.println((new AQuestion()).i); 
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 11.    } 
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 12.  } 
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Select one correct answer
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a. Compiler error complaining about access restriction of private variables of AQuestion.
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b. Compiler error complaining about forward referencing.
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c. No Compilation error - The output is 0;
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d. No Compilation error - The output is 10;
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Q75
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What is the result of compiling the following program	
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 1.   public class Test { 
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 2.     public static void main(String args[]) { 
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 3.       System.out.println("Before Try"); 
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 4.       try { 
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 5.       } catch(java.io.IOException t) { 
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 6.          System.out.println("Inside Catch"); 
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 7.       } 
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 8.       System.out.println("At the End"); 
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 9.     } 
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 10.  }
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Select one correct answer
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a. No Compilation Error.
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b. Compiler error complaining about the catch block where no IOException object can ever be thrown.
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c. Compiler error - IOException not found. It must be imported in the first line of the code.
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d. No compiler error. The lines "Before Try" and "At the end" are printed on the screen.
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Q76
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Read the following snippet carefully	
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 1.  public synchronized void someMethod() { 
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 2.      //lots of code 
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 3.      try { 
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 4.        Thread.sleep(500); 
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 5.      } catch(InterruptedException e) { 
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 6.         //do some things here. 
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 7.      } 
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 8.      //more and more code here 
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 9.  }
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Select all correct answers
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a. The code causes compilation error  - sleep  cannot be called inside synchronized methods.
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b. The Thread sleeps for at least 500 milliseconds in this method if not interrupted.
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c. When the thread "goes to sleep" it releases the lock on the object.
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d. The "sleeping" Threads always have the lock on the Object.
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Q77
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What will be the result of attempt to compile and the run the following code
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 1.  public class ADirtyOne { 
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 2.    public static void main(String args[]) { 
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 3.     System.out.println(Math.abs(Integer.MIN_VALUE)); 
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 4.    } 
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 5.  }
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Select one correct answer
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a. Causes a compilation error.
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b. Causes no error and the value printed on the screen is less than zero.
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c. Causes no error and the value printed on the screen is one more than Integer.MAX_VALUE 
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d. Will throw a runtime exception due to overflow - Integer.MAX_VALUE is less in magnitue than Integer.MIN_VALUE.
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Q78
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What is the result of attempting to compile and run the following program
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 1.   public class Test {
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 2.     public void method(Object o) { 
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 3.       System.out.println("Object Version"); 
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 4.     }
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 5.     public void method(String s) { 
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 6.       System.out.println("String Version"); 
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 7.     }
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 8.     public static void main(String args[]) { 
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 9.       Test test = new Test(); 
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 10.      test.method(null); 
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 11.    }
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 12.  }
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Select one correct answer
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a. The code does not compile.
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b. The code compiles cleanly and shows "Object Version".
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c. The code compiles cleanly and shows "String Version".
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d. The code throws an Exception at Runtime.
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Q79
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What is the result of attempting to compile the following program
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 1.   public class Test {
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 2.     public void method(StringBuffer sb) { 
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 3.       System.out.println("StringBuffer Verion"); 
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 4.     }
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 5.     public void method(String s) { 
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 6.       System.out.println("String Version"); 
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 7.     }
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 8.     public static void main(String args[]) { 
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 9.       Test test = new Test(); 
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 10.      test.method(null); 
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 11.    }
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 12.  }
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Select one correct answer
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a. The code does not compile.
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b. The code compiles correctly and shows "StringBuffer Version".
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c. The code compiles correctly and shows "String Version".
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d. The code throws an Exception at Runtime.
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Q80
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What is the requirement of the class which implements the following Interface
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 1.  public interface Test { 
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 2.      void someMethod(); 
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 3.  }
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Select all correct answers
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a. Should have someMethod which must be necessarily declared as public.
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b. Should have someMethod which could be "friendly" or public
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c. Should have someMethod which should not throw any checked exceptions.
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d. Should have someMethod which cannot be sychronized as sychronized is not in the signature of the interface definition.
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Q81
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What is the result of attempting to compile and run the following program?	
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 1.   public class AStringQuestion { 
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 2.     static String s1; 
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 3.     static String s2;
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 4.     public static void main(String args[]) { 
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 5.       s2 = s1+s2; 
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 6.       System.out.println(s2); 
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 7.     } 
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 8.   }
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[Select one correct answer]
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a. Will cause a compilation error.
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b. Runtime Execption - NullPointerException in the 2nd line of the main method.
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c. Will compile successfully and print "nullnull" on the screen.
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d. Will compile successfully and print an empty line on the screen.
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Q82
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What is the result of attempting to compile and run the following program?
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 1.   import java.io.*;
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 2.   public class OutOut { 
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 3.     public static void main(String args[]) throws IOException { 
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 4.       PrintStream pr = new PrintStream(new FileOutputStream("outfile")); 
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 5.       System.out = pr; 
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 6.       System.out.println("Lets see what I s