18. Substrings



Answer:
if ( line.length() > colNum && line.charAt( colNum ) != ' ' )
  System.out.println( counter + ":\t" + line );



The short-circuit operation of && means that line.length() > colNum is tested first. 
 If this result is false, then the next part of the condition is not tested (since the result of AND will be false  
 regardless of its result). So line.charAt( colNum ) is only performed when it is certain that the line contains a character at index colNum.


Substrings





    









    





    

    

    

    

    

        
A substring of a string is a sequence of characters from the original string. The characters are in the same order as in the original string and no characters are skipped. For example, the following are all substrings
            of the string "applecart":

        
apple
cart
pple
e
lecar


        
You have previously seen (in chapter 11) the substring() method of String objects:

        
public String substring(int beginIndex )


    

    

        
This method creates a new substring that consists of the characters from character number beginIndex to the end of the string. For example

        
"applecart".substring(5)


        
contains the characters "cart" .

        
bug Remember: character numbering starts with zero. The leftmost character of a string is character zero. The rightmost character is character length-1.

    

    





Question 18:
What is printed by the following code:
    String source = "applecart";
String sub = source.substring(6);
System.out.println( sub );
System.out.println( source );