Java Regex Quantifiers
The quantifiers specify how often an element can occur. The symbols ?, *, + and {} define the quantity of the regular expressions.
Regex | Description |
X? | X occurs once or not at all |
X+ | X occurs once or more times |
X* | X occurs zero or more times |
X{n} | X occurs n times only |
X{n,} | X occurs n or more times |
X{y,z} | X occurs at least y times but less than z times |
Java Regex Quantifiers Example
package com.w3spoint;
import java.util.regex.Pattern;
public class RegexTest {
public static void main(String args[]){
System.out.println("? quantifier ....");
//true (a or j or n comes one time)
System.out.println(Pattern.matches("[ajn]?", "a"));
//false (a comes more than one time)
System.out.println(Pattern.matches("[ajn]?", "aaa"));
//false (a j and n comes more than one time)
System.out.println(Pattern.matches("[ajn]?", "aammmnn"));
//false (a comes more than one time)
System.out.println(Pattern.matches("[ajn]?", "aazzta"));
//false (a or j or n must come one time)
System.out.println(Pattern.matches("[ajn]?", "aj"));
System.out.println("+ quantifier ....");
//true (a or j or n once or more times)
System.out.println(Pattern.matches("[ajn]+", "a"));
//true (a comes more than one time)
System.out.println(Pattern.matches("[ajn]+", "aaa"));
//true (a or j or n comes more than once)
System.out.println(Pattern.matches("[ajn]+", "aammmnn"));
//false (z and t are not matching pattern)
System.out.println(Pattern.matches("[ajn]+", "aazzta"));
System.out.println("* quantifier ....");
//true (a or j or n may come zero or more times)
System.out.println(Pattern.matches("[ajn]*", "ajjjna"));
}
} |
package com.w3spoint; import java.util.regex.Pattern; public class RegexTest {
public static void main(String args[]){
System.out.println("? quantifier ....");
//true (a or j or n comes one time)
System.out.println(Pattern.matches("[ajn]?", "a"));
//false (a comes more than one time)
System.out.println(Pattern.matches("[ajn]?", "aaa"));
//false (a j and n comes more than one time)
System.out.println(Pattern.matches("[ajn]?", "aammmnn"));
//false (a comes more than one time)
System.out.println(Pattern.matches("[ajn]?", "aazzta"));
//false (a or j or n must come one time)
System.out.println(Pattern.matches("[ajn]?", "aj"));
System.out.println("+ quantifier ....");
//true (a or j or n once or more times)
System.out.println(Pattern.matches("[ajn]+", "a"));
//true (a comes more than one time)
System.out.println(Pattern.matches("[ajn]+", "aaa"));
//true (a or j or n comes more than once)
System.out.println(Pattern.matches("[ajn]+", "aammmnn"));
//false (z and t are not matching pattern)
System.out.println(Pattern.matches("[ajn]+", "aazzta"));
System.out.println("* quantifier ....");
//true (a or j or n may come zero or more times)
System.out.println(Pattern.matches("[ajn]*", "ajjjna"));
}
}
Output
? quantifier ....
true
false
false
false
false
+ quantifier ....
true
true
false
false
* quantifier ....
true |
? quantifier ....
true
false
false
false
false
+ quantifier ....
true
true
false
false
* quantifier ....
true