NoSuchFieldException when field exists

Question

I'm getting a java.lang.NoSuchFieldException when trying to run the following method:

 public void getTimes(String specialty, String day) {
    ArrayList<Tutor> withSpec = new ArrayList<Tutor>();
    for (Tutor t : tutorList){
        try {
            Time startTime = (Time)t.getClass().getField(day + "Start").get(t);
        } catch (NoSuchFieldException | SecurityException | IllegalAccessException ex) Logger.getLogger(DBHandler.class.getName()).log(Level.SEVERE, null, ex); }

The error is on the line Time startTime = (Time)t.getClass().getField(day + "Start").get(t);

I don't understand this error, because monStart is a field of the Tutor class:

Public class Tutor implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@Basic(optional = false)
@NotNull
@Column(name = "tutorID")
private Integer tutorID;

.... 

@Column(name = "monStart")
@Temporal(TemporalType.TIME)
 Date monStart;

I'm just learning to use reflection, so I'm sure this is some sort of a syntactical error...

Answer 1

The getField method will only find the field if it's public. You will need to use the getDeclaredField method instead, which will find any field that is declared directly on the class, even if it's not public.

Answer 2

According to the javadoc, Class.getField() "Returns a Field object that reflects the specified public member field of the class or interface represented by this Class object". Use getDeclaredField() if you want to access non-public fields.

Answer 3

Best solutions for getClass().getField() problem are:

1. Use getDeclaredField() instead of getField():

        String propertyName = "test";
        Class.forName(this.getClass().getName()).getDeclaredField(propertyName);

2. Replace "HelloWorld" with your class name:

        String propertyName = "name";
        HelloWorld.class.getDeclaredField(propertyName);

If you want to get the annotation length of the column:

HelloWorld.class.getDeclaredField(propertyName).getAnnotation(Column.class).length();

Answer 4

For any Android developers seeing this that still can't seem to fix the issue, check to see if Proguard is enabled. If it is, it's possible the class in question is being obfuscated and you'll need to add rules to prevent that from happening.

Answer 5

As mentioned in the accepted answer, using getDeclaredField will potentially solve your problem (in case the field wasn't declared as public).

If you are still getting the NoSuchFieldException, then it might be because that field is actually in the superclass! Indeed, if your class extends another class, then you will not get the inherited fields through the getDeclaredField method. Here is how to fix that problem:

String propertyName = "foo";
yourClass.getClass().getSuperClass().getDeclaredField(propertyName);