Check if a String Contains only Alphabets in Java using Regex

// Java Program to Check If String Contains Only Alphabets
// Using Regular Expression

// Main class
class GFG {

    // Method 1
    // To check String for only Alphabets
    public static boolean isStringOnlyAlphabet(String str)
    {

        return ((str != null) && (!str.equals(""))
                && (str.matches("^[a-zA-Z]*$")));
    }

    // Method 2
    // Main driver method
    public static void main(String[] args)
    {

        // Calling out methods over string
        // covering all scenarios

        // Use case 1
        System.out.println("Test Case 1:");
        // Input string
        String str1 = "GeeksforGeeks";
        System.out.println("Input: " + str1);

        System.out.println("Output: "
                           + isStringOnlyAlphabet(str1));

        // Use case 2
        // Checking for String with numeric characters
        System.out.println("\nTest Case 2:");
        // Input string
        String str2 = "Geeks4Geeks";
        System.out.println("Input: " + str2);
        System.out.println("Output: "
                           + isStringOnlyAlphabet(str2));

        // Use Case 3
        // Checking for null String
        System.out.println("\nTest Case 3:");
        // Input string
        String str3 = null;
        System.out.println("Input: " + str3);
        System.out.println("Output: "
                           + isStringOnlyAlphabet(str3));

        // Use Case 4
        // Checking for empty String
        System.out.println("\nTest Case 4:");
        // Input string
        String str4 = "";
        System.out.println("Input: " + str4);
        System.out.println("Output: "
                           + isStringOnlyAlphabet(str4));
    }
}