Numbers - Java - page 211

because these have a character at the front that loses its meaning if placed at the end, and
hence are not strictly palindromic. Further, palindromic forms of certain numbers are too
long to fit in Java's 64-bit long integer. These cause underflow, which is trapped. As a result,
an error message like “too big” is reported. [ 25 ] Having said all that, Example 5-11 shows the
code.

Example 5-11. Palindrome.java
public public class class Palindrome Palindrome {

public public static static boolean boolean verbose = true true ;

public public static static void void main ( String [] argv ) {

for for ( int int i = 0 ; i < argv . length ; i ++)

try try {

long long l = Long . parseLong ( argv [ i ]);

iif ( l < 0 ) {
System . err . println ( argv [ i ] + " -> TOO SMALL" );
continue

continue ;

}
System . out . println ( argv [ i ] + "->" + findPalindrome ( l ));
} catch catch ( NumberFormatException e ) {

System . err . println ( argv [ i ] + "-> INVALID" );
} catch catch ( IllegalStateException e ) {

System . err . println ( argv [ i ] + "-> " + e );

}

}

/** find a palindromic number given a starting point, by
* calling ourself until we get a number that is palindromic.
*/
static

static long long findPalindrome ( long long num ) {

iif ( num < 0 )
throw new IllegalStateException ( "negative" );

iif ( isPalindrome ( num ))
return

throw new

return num ;
iif ( verbose )
System . out . println ( "Trying " + num );
return

return findPalindrome ( num + reverseNumber ( num ));

}

/** The number of digits in Long.MAX_VALUE */
protected protected static static final final int int MAX_DIGITS = 19 ;

// digits array is shared by isPalindrome and reverseNumber,