SCJP Garbage collection, Operators and assignments

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QUESTION : 1
  
  What is the result that will be printed out here ?
       int i =  - 128;
       System.out.println((byte)i << 1);



1.    0
2. -256
3.  127
4. -127
5.   -1 

ANS : 2
   
   Though the value in i is cast to a byte 
   it reverts to an int as the result of the left shift
   which makes the value of i  - 256



QUESTION : 2

   What is the result of the following operation?
     int n = 8;
     n = n & n + 1;
     n<<=n/2;
    
1.  32
2.  12
3.   8
4.  24
5. 128
6.   0

ANS : 5
 
   The arithmetic + operator takes precedence over the 
   bitwise & operator so  8 & 9 = 8  
   Shifting 8 by four bits to the left gives you 128





QUESTION : 3
    
    Observe the code below
 	public class Test {
	int a[] = new int[4];
	  void aMethod()
	  {
	  int b = 0 , index;
	  a[a[b]] = a[b] =  b = 2;
	  index = ??? ;
          System.out.println(a[index]);
	  }
	 }
   What value assigned to the variable index will print a non zero result?

1. 0
2. 1
3. 2
4. 3

ANS : 1

   the operands are evaluated from left to right here 
   so in the expression a[a[b]] the value of b is 0 
   and a[0] also holds the value 0 when the expression
   is evaluated so the array element at index 0 is assigned
   the value 2.




QUESTION : 4

    Will this test evaluate to true?
        Object a = "hello";
        String b = "hello";
        if(a == b)
        System.out.println("equal");
        else
        System.out.println("not equal");
   

1. Yes
2. No

ANS : 1

    It does not matter if the object reference is of type Object
    this will still return true because both of them point to the
    same String object in the string pool. 
    



QUESTION : 5
    
     True or False. 
    The garbage collector is required to makes sure that all objects 
    held by soft references are garbage collected before the VM throws
    an OutOfMemoryError.
        

1. True
2. False


ANS : 1

   If the  VM finds itself unable to allocate memory for
   a new object it is required to kick start the garbage 
   collector and reclaim all objects that are not held
   by strong references  before throwing an OutOfMemoryError.


 
QUESTION : 6


    What will be the value of the variable x here
    int x = 8 | 12  ^ 8;


1.  4
2.  8
3. 12
4.  0

ANS : 3
      


QUESTION : 7

 
        What will be the value of the variable x here
         int x = 8 ^ 5  &  6;


1.  0
2.  4
3.  6
4.  8
5. 12

ANS : 5

     The precedence  of bitwise operators  
     is AND , XOR and OR 
     so 5 AND 6 is evaluated first which gives you 4.
     8 XOR 4 = 12   



QUESTION : 8


  What is the result that will be printed out
   public class Test {
    public static void main(String[] args)
     {
     int a =  -8;
     int b = ~ -33;
     a>>>=b;
     System.out.println(a);
     }
   }

1. 1
2. 8
3. -8
4. 0
5. 16

ANS : 3
 


QUESTION : 9

    Is this legal ?
  
       public class Test {
         public static void main(String[] args)
         {
         char c = 65;
         double d = 10;
         if(c==d)
         System.out.println("equal");
         else
         System.out.println("not equal");
         }
       }

1. No.
2. Yes.

ANS : 2

          

QUESTION : 10
   
       Select the valid assignments


1.int i = (int)16.2d;
2. byte b = (byte)(long)16.2;
3. byte b = 128;
4. float f = 16.2;
5. byte b = (int)16.2; 

ANS : 1,2,5

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