Check if a string contains only alphabets in Java using Lambda expression

Given a String, the task is to check whether a string contains only alphabets or not.

Examples:

Input : GeeksforGeeks
Output : True

Input : Geeks4Geeks
Output : False

Input : null
Output : False

The idea is to use isLetter() method of Character class.

Algorithm:

  1. Get the string
  2. Match the string:
    • Check if the string is empty or not. If empty, return false
    • Check if the string is null or not. If null, return false.
    • If the string is neither empty nor null,
      then check using Lambda Expression Character::isLetter().
  3. Return true if matched

Pseudocode:



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public static boolean isStringOnlyAlphabet(String str)
{
    return ((!str.equals(""))
            && (str != null)
            && (str.chars().allMatch(Character::isLetter)));
}

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Program: Checking if String contains only Alphabets.

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// Java program to check if String contains only Alphabets
// using Lambda Expression
  
class GFG {
  
    // Function to check String for only Alphabets
    public static boolean isStringOnlyAlphabet(String str)
    {
        return ((str != null)
                && (!str.equals(""))
                && (str.chars().allMatch(Character::isLetter)));
    }
  
    // Main method
    public static void main(String[] args)
    {
  
        // Checking for True case
        System.out.println("Test Case 1:");
  
        String str1 = "GeeksforGeeks";
        System.out.println("Input: " + str1);
        System.out.println("Output: " + isStringOnlyAlphabet(str1));
  
        // Checking for String with numeric characters
        System.out.println("\nTest Case 2:");
  
        String str2 = "Geeks4Geeks";
        System.out.println("Input: " + str2);
        System.out.println("Output: " + isStringOnlyAlphabet(str2));
  
        // Checking for null String
        System.out.println("\nTest Case 3:");
  
        String str3 = null;
        System.out.println("Input: " + str3);
        System.out.println("Output: " + isStringOnlyAlphabet(str3));
  
        // Checking for empty String
        System.out.println("\nTest Case 4:");
  
        String str4 = "";
        System.out.println("Input: " + str4);
        System.out.println("Output: " + isStringOnlyAlphabet(str4));
    }
}

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Output:

Test Case 1:
Input: GeeksforGeeks
Output: true

Test Case 2:
Input: Geeks4Geeks
Output: false

Test Case 3:
Input: null
Output: false

Test Case 4:
Input: 
Output: false

Check if a string contains only alphabets in Java using ASCII values
Check if a string contains only alphabets in Java using Regex

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