OBJECT-ORIENTED THINKING - Introduction to Java Programming: Comprehensive Version - page 397

40 }
41
42

// Return a new filtered string

43 return stringBuilder.toString();

44 }
45
46 /** Create a new string by reversing a specified string */
47 public static String reverse(String s) {
48 StringBuilder stringBuilder = new StringBuilder(s);
49

stringBuilder.reverse(); // Invoke reverse in StringBuilder

50 return stringBuilder.toString();

51 }
52 }

Enter a string: ab<c>cb?a
Ignoring nonalphanumeric characters,
is ab<c>cb?a a palindrome? true

Enter a string: abcc><?cab
Ignoring nonalphanumeric characters,
is abcc><?cab a palindrome? false

The filter(String s) method (lines 31-44) examines each character in string s and cop-
ies it to a string builder if the character is a letter or a numeric character. The filter method
returns the string in the builder. The reverse(String s) method (lines 47-51) creates a
new string that reverses the specified string s . The filter and reverse methods both return
a new string. The original string is not changed.
The program in Listing 5.14 checks whether a string is a palindrome by comparing pairs
of characters from both ends of the string. Listing 10.10 uses the reverse method in the
StringBuilder class to reverse the string, then compares whether the two strings are equal
to determine whether the original string is a palindrome.

10.26 What is the difference between StringBuilder and StringBuffer ?
10.27 How do you create a string builder from a string? How do you return a string from a
string builder?
10.28 Write three statements to reverse a string s using the reverse method in the
StringBuilder class.
10.29 Write three statements to delete a substring from a string s of 20 characters, start-
ing at index 4 and ending with index 10 . Use the delete method in the String-
Builder class.
10.30 What is the internal storage for characters in a string and a string builder?
10.31 Suppose that s1 and s2 are given as follows:

✓ ✓

Check

Point

StringBuilder s1 = new StringBuilder( "Java" );
StringBuilder s2 = new StringBuilder( "HTML" );

Show the value of s1 after each of the following statements. Assume that the state-
ments are independent.

a. s1.append( " is fun" );
b. s1.append(s2);