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Check if a string contains only alphabets in Java

• Last Updated : 02 Nov, 2022

Given a string, the task is to write a Java program to check whether the string contains only alphabets or not. If so, then print true, otherwise false.

Examples:

Input: GeeksforGeeks
Output: true
Explanation: The given string contains only alphabets so the output is true.

Input: GeeksforGeeks2020
Output: false
Explanation: The given string contains alphabets and numbers so the output is false.

Input: “”
Output: false
Explanation: The given string is empty so the output is false.

Method 1: This problem can be solved using the ASCII values. Please refer this article for this approach.

Method 2: This problem can be solved using Lambda expression. Please refer this article for this approach.

Method 3: This problem can be solved using Regular Expression. Please refer this article for this approach.

Method 4: This approach uses the methods of Character class in Java

• The idea is to iterate over each character of the string and check whether the specified character is a letter or not using Character.isLetter() method
• If the character is a letter then continue, else return false
• If we are able to iterate over the whole string, then return true.

Below is the implementation of the above approach:

Java

 `class` `GFG {`   `    ``// Function to check if a string` `    ``// contains only alphabets` `    ``public` `static` `boolean` `onlyAlphabets(` `      ``String str, ``int` `n)` `    ``{`   `        ``// Return false if the string` `        ``// has empty or null` `        ``if` `(str == ``null` `|| str == ``""``) {` `            ``return` `false``;` `        ``}`   `        ``// Traverse the string from` `        ``// start to end` `        ``for` `(``int` `i = ``0``; i < n; i++) {` `            ``// Check if the specified` `            ``// character is not a letter then` `            ``// return false,` `            ``// else return true` `            ``if` `(!Character` `                ``.isLetter(str.charAt(i))) {` `                ``return` `false``;` `            ``}` `        ``}` `        ``return` `true``;` `    ``}`   `    ``// Driver Code` `    ``public` `static` `void` `main(String args[])` `    ``{` `        ``// Given string str` `        ``String str = ``"GeeksforGeeks"``;` `        ``int` `len = str.length();`   `        ``// Function Call` `        ``System.out.println(` `          ``onlyAlphabets(str, len));` `    ``}` `}`

Output

`true`

Time Complexity: O(N), where N is the size of the given string.
Auxiliary Space: O(1), no extra space required so it is a constant.

Method 5 : Using contains() method and ArrayList

Java

 `import` `java.util.*;` `import` `java.lang.*;` `class` `Main{` `    ``// Function to check if a string` `    ``// contains only alphabets` `    ``public` `static` `boolean` `onlyAlphabets(String str, ``int` `n)` `    ``{` `        ``// Return false if the string` `        ``// has empty or null` `        ``if` `(str == ``null` `|| str == ``""``) {` `            ``return` `false``;` `        ``}` `        ``ArrayList alphabets = ``new` `ArrayList();` `        ``String alpha = ``"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"``;` `        ``for``(``int` `i=``0``;i

Output

`true`

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