How do I check if a character is uppercase?

Hello. I thought that since I've had such great help from the community I'll post another question. So the problem I'm encountering is that I have to check for two conditions, if the first character is 'm' and if the second character is uppercase. I'll post the decription of the exercise below in case you don't see it.

"So I was wondering if you could help me with some of these code challenges. As you might've seen when a member field name doesn't match the style we've talked about, I send an error about it. Let's write some code to validate the style of the field name.

I've added the method validatedFieldName it will return the validated field name. If the value passed in doesn't meet the requirements, throw an IllegalArgumentException. I'll keep you posted on the results every time you press check work."

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.indexOf(0) != 'm' /* || Character.isLowerCase(fieldName.indexOf(1)) */ ) {
     throw new IllegalArgumentException("Make sure the first charater is m and the second is uppercase.");
    }

    return fieldName;
  }

}