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String Matching with Wildcards
Wildcard Basics
Wildcards are special characters used to match patterns within strings. They are commonly used in search operations to find strings that follow a specific pattern.
Asterisk (*) Wildcard
The asterisk (*) wildcard matches zero or more characters in a string. It is useful for finding strings with varying lengths.
public class WildcardExample {
public static void main(String[] args) {
String pattern = "a*b";
String text = "acb";
System.out.println(text.matches(pattern)); // Output: true
}
}
Console Output:
true
Question Mark (?) Wildcard
Single Character Matching
The question mark (?) wildcard matches exactly one character. It's useful for finding strings where a specific character can vary.
public class WildcardExample {
public static void main(String[] args) {
String pattern = "a?c";
String text = "abc";
System.out.println(text.matches(pattern)); // Output: true
}
}
Console Output:
true
Combining Wildcards
Complex Pattern Matching
You can combine wildcards to create complex patterns for string matching. This allows for flexible search criteria.
public class WildcardExample {
public static void main(String[] args) {
String pattern = "a*b?d";
String text = "aabcd";
System.out.println(text.matches(pattern)); // Output: true
}
}
Console Output:
true
Character Classes
Defining Character Sets
Character classes allow you to define a set of characters to match within brackets []. This is useful for specifying multiple possible characters at a position.
public class WildcardExample {
public static void main(String[] args) {
String pattern = "[a-c]x";
String text = "bx";
System.out.println(text.matches(pattern)); // Output: true
}
}
Console Output:
true
Negating Character Classes
Excluding Characters
By using a caret (^) inside a character class, you can negate it, specifying characters that should not be matched.
public class WildcardExample {
public static void main(String[] args) {
String pattern = "[^a-c]x";
String text = "dx";
System.out.println(text.matches(pattern)); // Output: true
}
}
Console Output:
true
