JAVA EE: What is Regex character classes and how to use simple class and negation

Tuesday 28 November 2017

What is Regex character classes and how to use simple class and negation | Java Regex

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What is Regex character classes and how to use simple class and negation | Java Regex

RegexDemo1.java

import java.util.regex.Pattern;

/**
 * 
 * [abc] = if a or b or c returns true else false.
 *
 */
public class RegexDemo1
{
    public static void main(String[] args)
    {
        /*
         * Parameters:
         * 
         * regex - The expression to be compiled
         * 
         * input - The character sequence to be matched
         * 
         * Returns:
         * 
         * whether or not the regular expression matches on the input
         * 
         */
        
        System.out.println("[abc] matches a = " +   Pattern.matches("[abc]", "a"));
        System.out.println("[abc] matches b = " +   Pattern.matches("[abc]", "b"));
        System.out.println("[abc] matches c = " +   Pattern.matches("[abc]", "c"));
        System.out.println("[abc] matches z = " +   Pattern.matches("[abc]", "z"));
        System.out.println("[abc] matches aa = " +   Pattern.matches("[abc]", "aa"));
        System.out.println("[abc] matches abc = " +   Pattern.matches("[abc]", "abc"));
    }

}

Output

[abc] matches a = true
[abc] matches b = true
[abc] matches c = true
[abc] matches z = false
[abc] matches aa = false
[abc] matches abc = false

RegexDemo2.java

import java.util.regex.Pattern;

/**
 * 
 * [^abc] = if any character except a or b or c returns true else false.
 *
 */
public class RegexDemo2
{
    public static void main(String[] args)
    {
        /*
         * Parameters:
         * 
         * regex - The expression to be compiled
         * 
         * input - The character sequence to be matched
         * 
         * Returns:
         * 
         * whether or not the regular expression matches on the input
         * 
         */
        
        System.out.println("[^abc] matches a = " +   Pattern.matches("[^abc]", "a"));
        System.out.println("[^abc] matches b = " +   Pattern.matches("[^abc]", "b"));
        System.out.println("[^abc] matches c = " +   Pattern.matches("[^abc]", "c"));
        System.out.println("[^abc] matches z = " +   Pattern.matches("[^abc]", "z"));
        System.out.println("[^abc] matches zz = " +   Pattern.matches("[^abc]", "zz"));
        System.out.println("[^abc] matches zzz = " +   Pattern.matches("[^abc]", "zzz"));
    }

}

Output

[^abc] matches a = false
[^abc] matches b = false
[^abc] matches c = false
[^abc] matches z = true
[^abc] matches zz = false
[^abc] matches zzz = false