I think I already satisfied both exceptions. What is wrong with my code?

public class TeacherAssistant {

  public static String validatedFieldName(String fieldName) {
    // These things should be verified:
    // 1.  Member fields must start with an 'm'
    // 2.  The second letter in the field name must be uppercased to ensure camel-casing
    // NOTE:  To check if something is not equal use the != symbol. eg: 3 != 4
    if (fieldName.charAt(0) != 'm') {
       throw new IllegalArgumentException("Member fields must start with an 'm'.");
    }
    if (Character.isUpperCase(fieldName.charAt(1))) {
       throw new IllegalArgumentException("The second letter in the field name must be uppercased to ensure camel-casing.");
    }
    return fieldName;
  }

}