Suppose we have to match characters that belong to one class but not to another in a composite character class pattern. There is no separate operator for the subtraction operation. Subtraction is performed by using the intersection operator, &&, and a negated inner character class.

For example, consider the following composite character class:

[0-9&&[^3-6]] 

It will match the digits, 0 to 9, except the digits, 3 to 6. This character class can also be written as a union of two character classes:

[[0-2][7-9]] 

We can also just use a simple character class, as follows:

[0-27-9]  
  

In order to match all the English consonant uppercase letters, we can subtract five vowels from uppercase letters, such as in the following regex:

[A-Z&&[^AEIOU]] 

We can also reverse the order of the two sets used in the preceding regex and use the following regex:

[[^AEIOU]&&A-Z]  

Suppose we want to match all punctuation characters except four basic math operators: +, -, *, and /. We can use the following composite character class using the subtraction operation:

[p{Punct}&&[^+*/-]] 

Here is a test class that tests the preceding subtraction character class:

package example.regex; 
 
import java.util.regex.*; 
   
public class SubtractionExample 
{ 
  public static void main(String[] args) 
  { 
    final Pattern p = Pattern.compile("[\p{Punct}&&[^+*/-]]"); 
    final String[] arr = new String[] { 
      "!", "@", "#", "$", "%", "+", "-", "*", "/", "1", "M", "d" 
    }; 
 
    for (String s: arr)  
    { 
      Matcher m = p.matcher(s); 
      System.out.printf("[%s] %s%n", s, 
         (m.matches() ? "matches" : "does not match")); 
    } 
  } 
} 

This program produces the following output when we run it after compilation:

[!] matches 
[@] matches 
[#] matches 
[$] matches 
[%] matches 
[+] does not match 
[-] does not match 
[*] does not match 
[/] does not match 
[1] does not match 
[M] does not match 
[d] does not match 

As is evident from this output, it allows all the punctuation characters except the four listed math operators.