Program to remove consonants from a String

Given a string str, the task is to remove all the consonants from the string and then print the string.

Examples:

Input: str= “Welcome to geeksforgeeks”
Output: eoe o eeoee



Input: str= “What is your name?”
Output: a i ou ae?

Approach: Traverse all the characters of the string, if the character is a consonant then remove it from the final answer.

Below is the implementation of the above approach:

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// Java program to remove consonants from a String
import java.util.Arrays;
import java.util.List;
  
class Test {
  
    // function that returns true
    // if the character is an alphabet
    static boolean isAlphabet(char ch)
    {
        if (ch >= 'a' && ch <= 'z')
            return true;
        if (ch >= 'A' && ch <= 'Z')
            return true;
        return false;
    }
  
    // function to return the string after
    // removing all the consonants from it
    static String remConsonants(String str)
    {
        Character vowels[]
            = { 'a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U' };
  
        List<Character> al = Arrays.asList(vowels);
  
        StringBuffer sb = new StringBuffer(str);
  
        for (int i = 0; i < sb.length(); i++) {
  
            if (isAlphabet(sb.charAt(i))
                && !al.contains(sb.charAt(i))) {
                sb.replace(i, i + 1, "");
                i--;
            }
        }
  
        return sb.toString();
    }
  
    // Driver method to test the above function
    public static void main(String[] args)
    {
        String str
            = "GeeeksforGeeks - A Computer Science Portal for Geeks";
  
        System.out.println(remConsonants(str));
    }
}

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Output:

eeeoee - A oue iee oa o ee

Below is another program using Regular Expressions in Java

Java

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// Java program to remove consonants from a String
  
class Test
{    
    static String remVowel(String str)
    {
         return str.replaceAll("[BCDFGHJKLMNPQRSTVXZbcdfghjklmnpqrstvxz]", "");
    }
      
    // Driver method to test the above function
    public static void main(String[] args) 
    {
        String str = "GeeeksforGeeks - A Computer Science Portal for Geeks";
          
        System.out.println(remVowel(str));
    }
}

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C#

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// C# program to remove consonants from a String
using System; 
using System.Text.RegularExpressions;
  
class GFG
    static String remVowel(String str)
    {
        return Regex.Replace(str, "[BCDFGHJKLMNPQRSTVXZbcdfghjklmnpqrstvxz]", "");
    }
      
    // Driver code
    public static void Main() 
    {
        String str = "GeeeksforGeeks - A Computer Science Portal for Geeks";
          
        Console.WriteLine(remVowel(str));
    }
}
  
// This code is contributed by Rajput-Ji

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Output:

eeeoee - A oue iee oa o ee

Time complexity : O(n) where n is the length of string



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Improved By : VishalBachchas, Rajput-Ji