Question

How to use X{n,m} , X{n,m}? and X{n,m}+ regular expressions (REGEX) in Java

Answer 1

package javaapplication1;
   
import java.util.regex.Matcher;
import java.util.regex.Pattern;
   
public class Example {
    public static void main(String[] args) {
        // X{n,m} , X{n,m}? and X{n,m}+  (X at least n but not more than m times)
        searchREGEX("a", "a{2,4}", "a{2,4}?", "a{2,4}+");
    }
       
    private static void searchREGEX(String input, String... regex_list) {
        for (String regex : regex_list) {
            Pattern pattern = Pattern.compile(regex);
            Matcher matcher = pattern.matcher(input);
    
            boolean found = false;
            while (matcher.find()) {
               System.out.println(String.format("%s: Found" + " \"%s\" " + "from index %d to %d",
                                       regex, matcher.group(), matcher.start(), matcher.end()));
               found = true;
            }
            System.out.println();
            if (!found) 
                System.out.println("Not found");
        }
    }
}
   
   
/*
run:
    
Not found

Not found

Not found
    
*/

 

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Answer 2

package javaapplication1;
   
import java.util.regex.Matcher;
import java.util.regex.Pattern;
   
public class Example {
    public static void main(String[] args) {
        // X{n,m} , X{n,m}? and X{n,m}+  (X at least n but not more than m times)
        searchREGEX("aaa", "a{2,4}", "a{2,4}?", "a{2,4}+");
    }
       
    private static void searchREGEX(String input, String... regex_list) {
        for (String regex : regex_list) {
            Pattern pattern = Pattern.compile(regex);
            Matcher matcher = pattern.matcher(input);
    
            boolean found = false;
            while (matcher.find()) {
               System.out.println(String.format("%s: Found" + " \"%s\" " + "from index %d to %d",
                                       regex, matcher.group(), matcher.start(), matcher.end()));
               found = true;
            }
            System.out.println();
            if (!found) 
                System.out.println("Not found");
        }
    }
}
   
   
/*
run:
    
a{2,4}: Found "aaa" from index 0 to 3

a{2,4}?: Found "aa" from index 0 to 2

a{2,4}+: Found "aaa" from index 0 to 3
    
*/

 

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Answer 3

package javaapplication1;
   
import java.util.regex.Matcher;
import java.util.regex.Pattern;
   
public class Example {
    public static void main(String[] args) {
        // X{n,m} , X{n,m}? and X{n,m}+  (X at least n but not more than m times)
        searchREGEX("aaaa", "a{2,4}", "a{2,4}?", "a{2,4}+");
    }
       
    private static void searchREGEX(String input, String... regex_list) {
        for (String regex : regex_list) {
            Pattern pattern = Pattern.compile(regex);
            Matcher matcher = pattern.matcher(input);
    
            boolean found = false;
            while (matcher.find()) {
               System.out.println(String.format("%s: Found" + " \"%s\" " + "from index %d to %d",
                                       regex, matcher.group(), matcher.start(), matcher.end()));
               found = true;
            }
            System.out.println();
            if (!found) 
                System.out.println("Not found");
        }
    }
}
   
   
/*
run:
    
a{2,4}: Found "aaaa" from index 0 to 4

a{2,4}?: Found "aa" from index 0 to 2
a{2,4}?: Found "aa" from index 2 to 4

a{2,4}+: Found "aaaa" from index 0 to 4
    
*/

 

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Answer 4

package javaapplication1;
   
import java.util.regex.Matcher;
import java.util.regex.Pattern;
   
public class Example {
    public static void main(String[] args) {
        // X{n,m} , X{n,m}? and X{n,m}+  (X at least n but not more than m times)
        searchREGEX("aaabaa", "a{2,4}", "a{2,4}?", "a{2,4}+");
    }
       
    private static void searchREGEX(String input, String... regex_list) {
        for (String regex : regex_list) {
            Pattern pattern = Pattern.compile(regex);
            Matcher matcher = pattern.matcher(input);
    
            boolean found = false;
            while (matcher.find()) {
               System.out.println(String.format("%s: Found" + " \"%s\" " + "from index %d to %d",
                                       regex, matcher.group(), matcher.start(), matcher.end()));
               found = true;
            }
            System.out.println();
            if (!found) 
                System.out.println("Not found");
        }
    }
}
   
   
/*
run:
    
a{2,4}: Found "aaa" from index 0 to 3
a{2,4}: Found "aa" from index 4 to 6

a{2,4}?: Found "aa" from index 0 to 2
a{2,4}?: Found "aa" from index 4 to 6

a{2,4}+: Found "aaa" from index 0 to 3
a{2,4}+: Found "aa" from index 4 to 6
    
*/

 

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