• Post Reply Bookmark Topic Watch Topic
  • New Topic
programming forums Java Mobile Certification Databases Caching Books Engineering Micro Controllers OS Languages Paradigms IDEs Build Tools Frameworks Application Servers Open Source This Site Careers Other Pie Elite all forums
this forum made possible by our volunteer staff, including ...
Marshals:
  • Campbell Ritchie
  • Ron McLeod
  • Rob Spoor
  • Tim Cooke
  • Junilu Lacar
Sheriffs:
  • Henry Wong
  • Liutauras Vilda
  • Jeanne Boyarsky
Saloon Keepers:
  • Jesse Silverman
  • Tim Holloway
  • Stephan van Hulst
  • Tim Moores
  • Carey Brown
Bartenders:
  • Al Hobbs
  • Mikalai Zaikin
  • Piet Souris

Marcus Green Exam 2 question 48

 
Greenhorn
Posts: 10
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
Here is the question:
Question 48)
Given the following variables
char c = 'c';
int i = 10;
double d = 10;
long l = 1;
String s = "Hello";
Which of the following will compile without error?
1)c=c+i;
2)s+=i;
3)i+=s;
4)c+=s;

Marcus says the only correct answer is 2. However, I am also able to successfully compile and execute answer 1. When I run it, I get the answer "m". Am I missing anything here?
 
Ranch Hand
Posts: 1070
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
I tried some test code just to double check and Marcus is correct.
1. False, c gets promoted to an int and then you try to assign back to a char.
2. True
3. False, trying to make string into an int
4. False, trying to make a string into a char
Try this code and see what you get:

If you are making it work, then post your code that is doing it so we can take a look at it.
Bill
 
Leon Webster
Greenhorn
Posts: 10
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
OOPs.
I saw (and coded) "c += i" rather than c = c+i;
Here is the code:
public class MyTest{
char c = 'c';
int i = 10;
public static void main(String[] args){
MyTest mt = new MyTest();
mt.c += mt.i;
System.out.println(mt.c);
}
}
Sorry for the confusion.
Leon
 
bill bozeman
Ranch Hand
Posts: 1070
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
No problem, easy one to make a mistake. Points out how += has an implicit cast back to the original value so char += int will work becuase it is the same as saying char = (char)(char + int)

Bill
 
Greenhorn
Posts: 5
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
However the string concatenation operator works only for string objects. Can you use it for concatening string and integer as in
s+=i?
Thanks
 
bill bozeman
Ranch Hand
Posts: 1070
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
sthorat,
You can use the shortcut += with String objects as long as you are forcing it back to a String so you can say:
String += int
but you can't say:
int += String
The reason is that whenever you use the "+" operator with a String object you get a String object as a result and you can cast a primitive to an object.
Bill
 
With a little knowledge, a cast iron skillet is non-stick and lasts a lifetime.
reply
    Bookmark Topic Watch Topic
  • New Topic