Special characters are those characters that are neither a letter nor a number. Whitespace is also not considered a special character. Examples of special characters are:- !(exclamation mark), , (comma), #(hash), etc.
Methods:
- Using Character class
- Using regular expressions
- Using contains() method
Method 1: Using Character class
The approach is as follows:
- Iterate through all the characters of the string.
- Alongside we will be checking each character for being a letter, a digit, or whitespace using the java character class.
- It is found to be none of the above signifying special characters.
- Parallelly we will maintain a counter for special character count.
- Lastly, print and display the required count or special characters as per the need.
Example
Java
// Java Program to Check Whether String contains Special// Characters Using Character Class// Importing input output classesimport java.io.*;// Main classclass GFG { // Method 1 // Main driver method public static void main(String[] args) { // Declaring and initializing count for // special characters int count = 0; // Input custom string String s = "!#$GeeeksforGeeks.Computer.Science.Portal!!"; // Iterating through the string // using standard length() method for (int i = 0; i < s.length(); i++) { // Checking the character for not being a // letter,digit or space if (!Character.isDigit(s.charAt(i)) && !Character.isLetter(s.charAt(i)) && !Character.isWhitespace(s.charAt(i))) { // Incrementing the countr for spl // characters by unity count++; } } // When there is no special character encountered if (count == 0) // Display the print statement System.out.println( "No Special Characters found."); else // Special character/s found then // Display the print statement System.out.println( "String has Special Characters\n" + count + " " + "Special Characters found."); }} |
Output
String has Special Characters 8 Special Characters found.
Time Complexity: O(N)
Auxiliary Space: O(N)
Method 2: Using regular expressions
- Create a regular expression that does not match any letters, digits, or whitespace.
- We will use Matcher class in accordance with regular expression with our input string.
- Now, if there exist any ‘character matches’ with the regular expression then the string contains special characters otherwise it does not contain any special characters.
- Print the result.
Java
// Java Program to Check Whether String contains Special// Characters using Regex classes// Importing regex classes from java.util package to// match a specific patternimport java.util.regex.Matcher;import java.util.regex.Pattern;// Main classpublic class GFG { // Main driver method public static void main(String[] args) { // Declaring and initializing strings randomly // with input characters // Custom Input as String 1 String s1 = "GeeksForGeeks"; // Creating regex pattern by // creating object of Pattern class Pattern p = Pattern.compile( "[^a-z0-9 ]", Pattern.CASE_INSENSITIVE); // Creating matcher for above pattern on our string Matcher m = p.matcher(s1); // Now finding the matches for which // let us set a boolean flag and // imposing find() method boolean res = m.find(); // Output will be based on boolean flag // If special characters are found if (res) // Display this message on the console System.out.println( "String1 contains Special Characters"); // If we reach here means no special characters are // found else // Display this message on the console System.out.println( "No Special Characters found in String 1"); // Custom Input as String 2 String s2 = "!!Geeks.For.Geeks##"; // Creating matcher for above pattern on our string // by creating object of matcher class Matcher m2 = p.matcher(s2); // Finding the matches using find() method boolean res2 = m2.find(); // If matches boolean returns true if (res2) // Then print and display that special // characters are found System.out.println( "String 2 contains Special Characters"); // If not else // Then Display the print statement below System.out.println( "No Special Characters found in String 2"); }} |
Output
No Special Characters found in String 1 String 2 contains Special Characters
Time Complexity: O(N)
Auxiliary Space: O(N)
Method 3 : Using contains() method
Java
// Java Program to Check Whether String contains Special Charactersimport java.io.*;import java.util.*;// Main classclass Main{ // Method 1 // Main driver method public static void main(String[] args) { // Declaring and initializing count for // special characters int count = 0; ArrayList<Character> a = new ArrayList<Character>(); String b="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"; for(int i=0;i<b.length();i++) { a.add(b.charAt(i)); } // Input custom string String s = "!#$GeeeksforGeeks.Computer.Science.Portal!!"; // Iterating through the string // using standard length() method for (int i = 0; i < s.length(); i++) { // Checking the character for not being a // letter,digit or space if (!a.contains(s.charAt(i)) && !Character.isWhitespace(s.charAt(i))) { // Incrementing the countr for spl // characters by unity count++; } } // When there is no special character encountered if (count == 0) // Display the print statement System.out.println("No Special Characters found."); else // Special character/s found then // Display the print statement System.out.println("String has Special Characters\n" + count + " "+ "Special Characters found."); }} |
Output
String has Special Characters 8 Special Characters found.
