I don't Know what I got Wrong

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


    // isUpperCase(Uppercase)?

    if (fieldName.indexOf(0) != 'm')
    {throw new IllegalArgumentException("the field name must starts with m");
    }
    if (Character.isUpperCase(fieldName.indexOf(1)) = false) 
    {throw new IllegalArgumentException("this fiels must be upper case");}



    return fieldName;
  }

}