Exceptions, Assertions, and Threads - Java 6 - page 186

LISTING 7.1 Continued

24: return;
25: }
26: }

The output of this program is as follows:

0 10 17 13 29 38 2 25 **
120 112 15 19 24 20 30 12 **
106 25 125 69 176 **

Line 15 of the program reads two characters from code , the string that was sent to the
readLine() method, by calling the string's substring( int , int ) method.

NOTE

In the substring() method of the String class, you select a sub-
string in a somewhat counterintuitive way. The first argument spec-
ifies the index of the first character to include in the substring, but
the second argument does not specify the last character. Instead,
the second argument indicates the index of the last character plus
1. A call to substring(2, 5) for a string would return the charac-
ters from index position 2 to index position 4.

The two-character substring contains a hexadecimal number stored as a String . The
Integer class method parseInt can be used with a second argument to convert this
number into an integer. Use 16 as the argument for a hexadecimal (base 16) conversion,
8 for an octal (base 8) conversion, and so on.

In the HexReader application, the hexadecimal FF is used to fill out the end of a sequence
and should not be displayed as a decimal value. This is accomplished by using a try -
finally block in lines 13-23 of Listing 7.1.

The try - finally block causes an unusual thing to happen when the return statement is
encountered at line 18. You would expect return to cause the readLine() method to be
exited immediately.

Because it is within a try - finally block, the statement within the finally block is exe-
cuted no matter how the try block is exited. The text “**” is displayed at the end of a
line of decimal values.