MATHEMATICAL FUNCTIONS, CHARACTERS, AND STRINGS - Introduction to Java Programming: Comprehensive Version - page 136

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We l

Indices
Message

c ome t o J a v a

message.substring(0, 11) message.substring(11)

F IGURE 4.2

The substring method obtains a substring from a string.

Note
If beginIndex is endIndex , substring(beginIndex, endIndex) returns an
empty string with length 0 . If beginIndex > endIndex , it would be a runtime error.

beginIndex <= endIndex

4.4.9 Finding a Character or a Substring in a String
The String class provides several versions of indexOf and lastIndexOf methods to find
a character or a substring in a string, as shown in Table 4.10.

T ABLE 4.10

The String class contains the methods for finding substrings.

Method Description
index(ch) Returns the index of the first occurrence of ch in the string. Returns -1 if not matched.
indexOf(ch, fromIndex) Returns the index of the first occurrence of ch after fromIndex in the string. Returns -1 if not matched.
indexOf(s) Returns the index of the first occurrence of string s in this string. Returns -1 if not matched.
indexOf(s, fromIndex) Returns the index of the first occurrence of string s in this string after fromIndex . Returns -1 if not
matched.
lastIndexOf(ch) Returns the index of the last occurrence of ch in the string. Returns -1 if not matched.
lastIndexOf(ch, fromIndex) Returns the index of the last occurrence of ch before fromIndex in this string. Returns -1 if not
matched.

Returns the index of the last occurrence of string s . Returns -1 if not matched. lastIndexOf(s)

Returns the index of the last occurrence of string s before fromIndex . Returns -1 if not matched.

lastIndexOf(s, fromIndex)

For example,

"Welcome to Java".indexOf('W') returns 0 .
"Welcome to Java".indexOf('o') returns 4 .
"Welcome to Java".indexOf('o', 5) returns 9 .
"Welcome to Java".indexOf("come") returns 3 .
"Welcome to Java".indexOf("Java", 5) returns 11 .
"Welcome to Java".indexOf("java", 5) returns -1 .

indexOf

"Welcome to Java".lastIndexOf('W') returns 0 .
"Welcome to Java".lastIndexOf('o') returns 9 .
"Welcome to Java".lastIndexOf('o', 5) returns 4 .
"Welcome to Java".lastIndexOf("come") returns 3 .
"Welcome to Java".lastIndexOf("Java", 5) returns -1 .
"Welcome to Java".lastIndexOf("Java") returns 11 .

lastIndexOf

Suppose a string s contains the first name and last name separated by a space. You can use the
following code to extract the first name and last name from the string:

int k = s.indexOf( ' ' );
String firstName = s.substring( 0 , k);
String lastName = s.substring(k + 1 );