You can use Java regular expressions to check if a String has only alphabets as follows:

package demo;

public class StringDemo {

public static void main(String[] args) { 
    String str = "HelloWorld"; 
    String regex = "^\[a-zA-Z\]+$"; 
    boolean matches = str.matches(regex); 
    System.out.println(matches);
 } 
}

The above code will print true when you run it. If you change the String str to have any other characters like numbers or special characters, it will print false.