if(Character.isJavaIdentifierStart('A')){ System.out.println("'A' can be a valid first character in a Java identifier."); }
if(Character.isJavaIdentifierStart('@')){ System.out.println("'@' can be a valid first character in a Java identifier."); }Output: '@' cannot be a valid first character in a Java identifier. The isJavaIdentifierStart method belongs to the java.lang.Character package library.