Lambda expressions basically express instances of functional interfaces (An interface with a single abstract method is called functional interface. An example is java.lang.Runnable). lambda expressions implement the only abstract function and therefore implement functional interfaces.
Given a String, we just need to iterate over characters again the task is to check whether a string contains only alphabets or not for which primarily we will check edge cases whether the string is present or not and should not be null, we will simply return false as there is no way to deal with that string. When the above condition is not fulfilled we will make use of lambda expression method isLetter() to check for only characters are there or not, and will return a corresponding boolean value.
Illustrations:
Input : Lazyroar Output : True
Input : Geeks4Geeks Output : False
Input : null Output : False
Concept: The idea is to use isLetter() method of Character class.
Algorithm:
- Get the string
- 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().- Return true if matched
Pseudocode for the above-proposed algorithm is as follows:
public static boolean isStringOnlyAlphabet(String str)
{
return ((!str.equals("")) && (str != null) && (str.matches("^[a-zA-Z]*$")));
}
Example:
Java
// Java program to check if String contains only Alphabets// Using Lambda Expressionclass GFG { // Method 1 // To check String for only Alphabets public static boolean isStringOnlyAlphabet(String str) { return ( (str != null) && (!str.equals("")) && (str.chars().allMatch(Character::isLetter))); } // Method 2 // Main driver method public static void main(String[] args) { // Calling method over different strings // justifying all use-cases possible // Display message System.out.println("Test Case 1:"); String str1 = "Lazyroar"; System.out.println("Input: " + str1); // Calling over above string: Lazyroar 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); // Calling over above string: Geeks4Geeks System.out.println("Output: " + isStringOnlyAlphabet(str2)); // Checking for null String System.out.println("\nTest Case 3:"); String str3 = null; System.out.println("Input: " + str3); // Calling over above string: null System.out.println("Output: " + isStringOnlyAlphabet(str3)); // Checking for empty String System.out.println("\nTest Case 4:"); String str4 = ""; System.out.println("Input: " + str4); // Calling over above string "" System.out.println("Output: " + isStringOnlyAlphabet(str4)); }} |
Test Case 1: Input: Lazyroar Output: true Test Case 2: Input: Geeks4Geeks Output: false Test Case 3: Input: null Output: false Test Case 4: Input: Output: false
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