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Marcus Exam2 #46

 
Greenhorn
Posts: 14
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Given,
String s = "Hello";
long l = 99;
double d = 1.11;
int i = 1;
int j = 0;
which lines below would compile?
1) j=i<<s;>
2)j= i<< j;
3)j=i<<d;>
4)j=i<<1;
Answeris 2 and 4
can some one explain??

Also, is this statement true?
"An interface cannot be instantiated"
thank you
 
Ranch Hand
Posts: 66
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Hi,
The type of each of the operands in Shift operation must be primitive integral type(short,byte,int,long), otherwise compiler error occurs. 1 & 3 use a String & a double which are not allowed. so the ans 2 & 4 are correct. Hope it helps.
Your options are not clear. I had the same problem with one of my Question & Maha anna told me that whenever we use relational operators we should leave space before & after them. otherwise they mess up.
Thanks,
Kiran.
 
Greenhorn
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Here is the actual question:
Given the following variables which of the following lines will compile without error?
String s = "Hello";
long l = 99;
double d = 1.11;
int i = 1;
int j = 0;
1) j= i << s;
2) j= i << j;
3) j=i << d;
4) j=i << l;
1) Wrong- because the shift cannot be a String
2) Correct- int can be used for both operands
3) Wrong- because the shift cannot be a double
4) Correct- the shift can be a long, the actual shift will be l%32 since the type of i is int. The type of the result depends on the type of the first operand. So if it had been j=l>>i; that would not compile because it would result in a long whereas j is an int.
[This message has been edited by lstrite (edited August 05, 2000).]
 
Ranch Hand
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The reason 1 and 3 are NOT correct is that the result of applying a relational operator is of type boolean. A boolean type cannot be assigned to ANY other type.
Interfaces CANNOT be instantiated. A class can implement the interface and that class can then be instantiated.
 
lstrite
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Answers 1 & 3 were not supposed to be relational, they are supposed to be shift,it just did not print them right.
For interfaces, they cannot be instantiated, but you can create a reference and it can hold any object that implements the interface such as this:
Runnable r = new myClassThatImplementsRunnable();
But the interface is self cannot be instantiated:
Runnable r = new Runnable; //Wrong
 
cowboy55
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Thank you all for your kinda explanations.
I understand it now.
regards
 
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