Java: Remove all non-alphanumeric characters from a given string

Last update on May 24 2025 12:58:57 (UTC/GMT +8 hours)

21. Remove Non-Alphanumeric

Write a Java program to remove all non-alphanumeric characters from a given string.

Sample Solution-1:

Java Code:

public class test {
 
   public static void main(String[] args) {	   
	    String text ="Java Exercises";
		System.out.println("Original string: "+text);
		System.out.println("After removing all non-alphanumeric characters from the said string: "+validate(text));
	    text ="Ex@^%&%(ercis*&)&es";
		System.out.println("\nOriginal string: "+text);
		System.out.println("After removing all non-alphanumeric characters from the said string: "+validate(text));	
        }

   public static String validate(String text) {
        return text.replaceAll("(?i)[^A-Z]", "");
   }
}

Sample Output:

Original string: Java Exercises
After removing all non-alphanumeric characters from the said string: JavaExercises

Original string: Ex@^%&%(ercis*&)&es
After removing all non-alphanumeric characters from the said string: Exercises

Pictorial Presentation:

Flowchart :

Sample Solution-2:

Java Code:

public class test {
 
   public static void main(String[] args) {	   
	    String text ="Java Exercises";
		System.out.println("Original string: "+text);
		System.out.println("After removing all non-alphanumeric characters from the said string: "+validate(text));
	    text ="Ex@^%&%(ercis*&)&es";
		System.out.println("\nOriginal string: "+text);
		System.out.println("After removing all non-alphanumeric characters from the said string: "+validate(text));	
        }

   public static String validate(String text) {
        return text.replaceAll("[^a-zA-Z]", "");
   }
}

Sample Output:

Original string: Java Exercises
After removing all non-alphanumeric characters from the said string: JavaExercises

Original string: Ex@^%&%(ercis*&)&es
After removing all non-alphanumeric characters from the said string: Exercises

Flowchart :

For more Practice: Solve these Related Problems:

• Write a Java program to filter a string to only include letters and digits using regex replacement.
• Write a Java program to iterate through a string and construct a new string containing only alphanumeric characters.
• Write a Java program to implement a method that strips out punctuation and symbols from a string.
• Write a Java program to compare the output of regex-based non-alphanumeric removal with manual character filtering.

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