STRINGS - Introduction to Java Programming - page 338

java.lang.String
+equals(s1: Object): boolean
+equalsIgnoreCase(s1: String):
boolean
+compareTo(s1: String): int

Returns true if this string is equal to string s1 .
Returns true if this string is equal to string s1 case
insensitive.
Returns an integer greater than 0 , equal to 0 , or less than 0
to indicate whether this string is greater than, equal to, or
less than s1 .
Same as compareTo except that the comparison is case
insensitive.
Returns true if the specified subregion of this string exactly
matches the specified subregion in string s1 .
Same as the preceding method except that you can specify
whether the match is case sensitive.

+compareToIgnoreCase(s1: String):
int
+regionMatches(index: int, s1: String,
s1Index: int, len: int): boolean
+regionMatches(ignoreCase: boolean,
index: int, s1: String, s1Index: int,
len: int): boolean
+startsWith(prefix: String): boolean
+endsWith(suffix: String): boolean

Returns true if this string starts with the specified prefix.
Returns true if this string ends with the specified suffix.

F IGURE 9.2

The String class contains the methods for comparing strings.

Note that parameter type for the equals method is Object . We will introduce the Object
class in Chapter 11. For now, you can replace Object by String for using the equals method
to compare two strings. For example, the following statements display true and then false .

String s1 = new String( "Welcome to Java" );
String s2 = "Welcome to Java" ;
String s3 = "Welcome to C++" ;
System.out.println(s1.equals(s2)); // true
System.out.println(s1.equals(s3)); // false

The compareTo method can also be used to compare two strings. For example, consider the
following code:

s1.compareTo(s2)

s1.compareTo(s2)

The method returns the value 0 if s1 is equal to s2 , a value less than 0 if s1 is lexicographi-
cally (i.e., in terms of Unicode ordering) less than s2 , and a value greater than 0 if s1 is lexi-
cographically greater than s2 .
The actual value returned from the compareTo method depends on the offset of the first
two distinct characters in s1 and s2 from left to right. For example, suppose s1 is abc and s2
is abg , and s1.compareTo(s2) returns -4 . The first two characters ( a vs. a ) from s1 and
s2 are compared. Because they are equal, the second two characters ( b vs. b ) are compared.
Because they are also equal, the third two characters ( c vs. g ) are compared. Since the char-
acter c is 4 less than g , the comparison returns -4 .

Caution
Syntax errors will occur if you compare strings by using comparison operators
> , >= , < , or <= . Instead, you have to use s1.compareTo(s2) .

Note
The equals method returns true if two strings are equal and false if they are not.
The compareTo method returns 0 , a positive integer, or a negative integer, depending
on whether one string is equal to, greater than, or less than the other string.

The String class also provides the equalsIgnoreCase , compareToIgnoreCase , and
regionMatches methods for comparing strings. The equalsIgnoreCase and