Java Remove Special Characters From String

Java Remove Special Characters From String | Except for alphanumeric characters remaining other characters are considered as the special characters. A number or an alphabet are not considered as special characters. For example “[email protected]#$%^&*” these characters are termed to be special characters. These characters need not be used everywhere, sometimes they might be unwanted.

Java String Replace Special Characters

Here, we will replace a single special character with an alphabet. To do this we can use the replaceAll() method available in Java. We will print both the actual string and string after the replacement so that the difference can be found easily.

public class Main {
   public static void main(String[] args) {
      String string = "[email protected] [email protected]";
      System.out.println("Actual String = " + string);

      string = string.replaceAll("[@]", "o");
      System.out.println("String after replacement = " + string);
   }
}

Output:

Actual String = [email protected] [email protected]
String after replacement = Know Program

In the above program, all “@” special character is replaced with the new character “o”. Hence the string “[email protected] [email protected]” becomes “Know Program.

How To Remove Special Characters From a String In Java Using Regex

Previously, we have replaced all the special characters in a string by using the replaceAll() method. We can do the same by using regular expressions. In the replaceAll() method we use ‘^’  this character selects the other characters except the character mentioned.

public class Main {
   public static void main(String[] args) {
      String string = "@Know$ ##Pr%ogram*";
      System.out.println("Actual String = " + string);

      string = string.replaceAll("[^a-zA-Z]", "");
      System.out.println("String after replacement = " + string);
   }
}

Output:

Actual String = @Know$ ##Pr%ogram*
String after replacement = KnowProgram

Java Replace All Special Characters From String

In this code, we use the if block in the loop to specify the character’s need, except for specified characters all the other characters will be removed. In the if condition we have written the code such that the characters other than a-z, A-Z, and 0-9 will be removed from the string. This code also removes spaces.

Java Program to Remove Spaces and Special Characters From String

public class Main {
   public static void main(String[] args) {
      String string = "Kno$*w;..,98   P7rogr5'a^m?6";
      for (int i = 0; i < string.length(); i++) {
         if ((string.charAt(i) < 'A' || string.charAt(i) > 'Z') && 
            (string.charAt(i) < 'a' || string.charAt(i) > 'z') &&
            (string.charAt(i) < '0' || string.charAt(i) > '9')) {
            string = string.substring(0, i) + string.substring(i + 1);
            i--;
         }
      }
      System.out.print(string);
   }
}

Output:

Know98P7rogr5am6

Java Remove Leading Special Characters From String

Now, we remove only the special character in the first place. We can do this by specifying the index. In order to remove the leading first special character, we create a static method removeLeading() which uses the StringBuilder class and used the if loop to remove the special character at the particular index.

public class Main {
   public static String removeLeading(String s) {
      StringBuilder sb = new StringBuilder(s);
      while ( sb.length() > 1 && sb.charAt(0) == '@' || 
            sb.charAt(0) == '!' || sb.charAt(0) == '#' || 
            sb.charAt(0) == '$' || sb.charAt(0) == '%') {
         sb.deleteCharAt(0);
      }
      return sb.toString();
   }

   public static void main(String[] args) {
      String string = "%Kno$*w;..,   Progr'a^m?0";
      System.out.println(removeLeading(string));
   }
}

Output:-

Kno$*w;.., Progr’a^m?0

Remove Last Special Character From String Java

In order to remove the last special characters from the string, we again create a static method removeLast() which uses the StringBuilder class to manipulate string by using if loop.

public class Main {

   public static String removeLast(String s) {
      StringBuilder sb = new StringBuilder(s);
      while (sb.length() > 1 && sb.charAt(sb.length() - 1) == '@' || 
            sb.charAt(sb.length() - 1) == '!'|| 
            sb.charAt(sb.length() - 1) == '#' || 
            sb.charAt(sb.length() - 1) == '$'|| 
            sb.charAt(sb.length() - 1) == '%') {
         sb.setLength(sb.length() - 1);
      }
      return sb.toString();
   }

   public static void main(String[] args) {
      String s = "%Kno$*w;..,   Progr'a^m#";
      System.out.println(removeLast(s));
   }
}

Output:

%Kno$*w;.., Progr’a^m

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