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Different Ways to Remove all the Digits from String in Java

Given alphanumeric string str, the task is to write a Java program to remove all the digit from this string and prints the modified string.

Examples:

Input: str = “GeeksForGeeks123”
Output: GeeksForGeeks
Explanation: The given string contains digits 1, 2, and 3. We remove all the digit and prints the modified string.

Input: str = “12Java”
Output: Java
Explanation: The given string contains digits 1 and 2. We remove all the digit and prints the modified string.

Method 1: Using String.toCharArray() method

1. Get the String to remove all the digit.
2. Convert the given string into a character array.
3. Initialize an empty string that stores the result.
4. Traverse the character array from start to end.
5. Check if the specified character is not digit then add this character into the result variable.
6. Now, print the result.

Below is the implementation of the above approach:

Java

 `// Java program to remove all the``// digit from string``class` `GFG {` `    ``// Function to remove all the digit``    ``// from string``    ``public` `static` `String removeAllDigit(String str)``    ``{``        ``// Converting the given string``        ``// into a character array``        ``char``[] charArray = str.toCharArray();``        ``String result = ``""``;` `        ``// Traverse the character array``        ``for` `(``int` `i = ``0``; i < charArray.length; i++) {` `            ``// Check if the specified character is not digit``            ``// then add this character into result variable``            ``if` `(!Character.isDigit(charArray[i])) {``                ``result = result + charArray[i];``            ``}``        ``}` `        ``// Return result``        ``return` `result;``    ``}` `    ``// Driver Code``    ``public` `static` `void` `main(String args[])``    ``{` `        ``// Given alphanumeric string str``        ``String str = ``"GeeksForGeeks123"``;` `        ``// Print the modified string``        ``System.out.println(removeAllDigit(str));``    ``}``}`

Output

`GeeksForGeeks`
• Time Complexity: O(N)
• Auxiliary Space: O(N)

Method 2: Using String.charAt() method

1. Get the String to remove all the digit.
2. Initialize an empty string that stores the result.
3. Traverse the String from start to end.
4. Check if the specified character is not digit then add this character into the result variable.
5. Now, print the result.

Below is the implementation of the above approach:

Java

 `// Java program to remove all the``// digit from string``class` `GFG {` `    ``// Function to remove all the digit``    ``// from string``    ``public` `static` `String removeAllDigit(String str)``    ``{``        ``String result = ``""``;` `        ``// Traverse the String from start to end``        ``for` `(``int` `i = ``0``; i < str.length(); i++) {` `            ``// Check if the specified character is not digit``            ``// then add this character into result variable``            ``if` `(!Character.isDigit(str.charAt(i))) {``                ``result = result + str.charAt(i);``            ``}``        ``}` `        ``// Return result``        ``return` `result;``    ``}` `    ``// Driver Code``    ``public` `static` `void` `main(String args[])``    ``{` `        ``// Given alphanumeric string str``        ``String str = ``"GeeksForGeeks123"``;` `        ``// Print the modified string``        ``System.out.println(removeAllDigit(str));``    ``}``}`

Output

`GeeksForGeeks`
• Time Complexity: O(N)
• Auxiliary Space: O(N)

Method 3: Using String.replaceAll() method

The idea is to use String.replaceAll() method that replaces all the sequence of characters that matches the given Regular Expression with the given replacement string.

Below is the implementation of the above approach:

Java

 `// Java program to remove all the``// digit from string``class` `GFG {` `    ``// Function to remove all the digit``    ``// from string``    ``public` `static` `String removeAllDigit(String str)``    ``{``        ``// Replaces all the sequence of characters``        ``// that matches the given regex with``        ``// the given replacement string``        ``return` `str.replaceAll(``"\\d"``, ``""``);``    ``}` `    ``// Driver Code``    ``public` `static` `void` `main(String args[])``    ``{` `        ``// Given alphanumeric string str``        ``String str = ``"GeeksForGeeks123"``;` `        ``// Print the modified string``        ``System.out.println(removeAllDigit(str));``    ``}``}`

Output

`GeeksForGeeks`
• Time Complexity: O(N)
• Auxiliary Space: O(1)

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