OBJECT-ORIENTED THINKING - Introduction to Java Programming: Comprehensive Version - page 389

The replaceAll , replaceFirst , and split methods can be used with a regular
expression. For example, the following statement returns a new string that replaces $ , + , or #
in a+b$#c with the string NNN .

String s = "a+b$#c" .replaceAll( "[$+#]" , "NNN" );
System.out.println(s);

replaceAll(regex)

Here the regular expression [$+#] specifies a pattern that matches $ , + , or # . So, the output
is aNNNbNNNNNNc .
The following statement splits the string into an array of strings delimited by punctuation marks.

String[] tokens = "Java,C?C#,C++" .split( "[.,:;?]" );

split(regex)

for ( int i = 0 ; i < tokens.length; i++)
System.out.println(tokens[i]);

In this example, the regular expression [.,:;?] specifies a pattern that matches . , , , : , ; , or
? . Each of these characters is a delimiter for splitting the string. Thus, the string is split into
Java , C , C# , and C++ , which are stored in array tokens .
Regular expression patterns are complex for beginning students to understand. For this
reason, simple patterns are introduced in this section. Please refer to Appendix H, Regular
Expressions, to learn more about these patterns.

further studies

10.10.5 Conversion between Strings and Arrays
Strings are not arrays, but a string can be converted into an array, and vice versa. To convert a
string into an array of characters, use the toCharArray method. For example, the following
statement converts the string Java to an array.

toCharArray

char [] chars = "Java" .toCharArray();

Thus, chars[0] is J , chars[1] is a , chars[2] is v , and chars[3] is a .
You can also use the getChars(int srcBegin, int srcEnd, char[] dst,
int dstBegin) method to copy a substring of the string from index srcBegin to index
srcEnd-1 into a character array dst starting from index dstBegin . For example, the fol-
lowing code copies a substring "3720" in "CS3720" from index 2 to index 6-1 into the
character array dst starting from index 4 .

char [] dst = { 'J' , 'A' , 'V' , 'A' , '1' , '3' , '0' , '1' };
"CS3720" .getChars( 2 , 6 , dst, 4 );

getChars

Thus, dst becomes {'J', 'A', 'V', 'A', '3', '7', '2', '0'} .
To convert an array of characters into a string, use the String(char[]) constructor or
the valueOf(char[]) method. For example, the following statement constructs a string
from an array using the String constructor.

String str = new String( new char []{ 'J' , 'a' , 'v' , 'a' });

The next statement constructs a string from an array using the valueOf method.

valueOf

String str = String.valueOf( new char []{ 'J' , 'a' , 'v' , 'a' });

10.10.6 Converting Characters and Numeric Values to Strings
Recall that you can use Double.parseDouble(str) or Integer.parseInt(str) to
convert a string to a double value or an int value and you can convert a character or a
number into a string by using the string concatenating operator. Another way of converting a