Java Review

[toad]

I am nearing the end of my first Java class and I am studying for my final. I was given a review quiz to study off of and I feel confident I know this stuff but would like a second opinion. If I am wrong if you could please point out why I am wrong so I can better understand this going into my final. The final is on Monday and thanks in advance for the help.

 1 . Suppose s1 and s2 are two strings. Which of the following statements or expressions are incorrect? 		 
a. String s3 = s1 - s2; 		
b. int i = s1.compareTo(s2); 		
c. char c = s1[0]; char c = s1.charAt(s1.length() - 1); 
e. a and c. 
           
Your choice is ___ E____   
       
2.  How can you initialize a string with "123"?
a. String[] string = {'1', '2', '3'}; 
b. String string = {'1', '2', '3'};		
c. String s =  "123"; 	
d. String s = new String("123"); 		
e. c and d are both fine, but c is better.

Your choice is ___E_____

3.  A subclass inherits _____________ from its superclasses.
a.private data 
b.protected data 
c.public data 
d.a and c 
e.b and c  
         
Your choice is _____E ___

4. When you implement a method that is defined in a superclass, you __________ the original method.

a. overload  
b. override 
c. copy 
d. call

Your choice is ___B_____

This is the first part of the reveiw sheet and is the only part I have filled in at this point. Thanks again for any insight. This forum has made my learning experience a lot easier.

[ShoeNinja]

I'm pretty sure that c is valid in #1. I would write a test program to make sure.

[toad]

I figured C was valid but wouldn't a be valid as well? If not can you briefly explain why it wouldn't? I am try to get a complete understanding of the concepts.

[hardwired]

1 - e
2 - e
3 - e
4 - b

String s3 = s1 - s2;

The "+" operator works for concatenation of/in strings. You cannot apply the "-" operator to strings.

char c = s1[0];

s1[0] is array notation and does not work for a String. For this to work the variable "s1" would have to be of type char[].

[toad]

I am a littile confused. At first it appears that you are saying I have answered correct (wouldn't that be great) but when I read the comment below the code snippets it looks like for problem 1 neither (a) or (c) would work so (e) would be incorrect. I maybe totally misreading what you posted. Thanks again.

1 - e
2 - e
3 - e
4 - b

String s3 = s1 - s2;

The "+" operator works for concatenation of/in strings. You cannot apply the "-" operator to strings.

char c = s1[0];

s1[0] is array notation and does not work for a String. For this to work the variable "s1" would have to be of type char[].

[hardwired]

Suppose s1 and s2 are two strings. Which of the following statements or expressions are incorrect?
Which statements are incorrect? Both a and c are incorrect.
Statement b is correct because String implements the Comparable interface.