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javareflectionfieldprivate

Get all private fields using reflection

I wonder is there a way to get all private fields of some class in Java and their type.

For example lets suppose I have a class:

class SomeClass {
    private String aaa;
    private SomeOtherClass bbb;
    private double ccc;
}

Now I would like to get all private fields (aaa, bbb, ccc) of class SomeClass (Without knowing name of all fields upfront) and check their type.

Solution

  • It is possible to obtain all fields with the method getDeclaredFields() of Class. Then you have to check the modifier of each fields to find the private ones:

    List<Field> privateFields = new ArrayList<>();
Field[] allFields = SomeClass.class.getDeclaredFields();
for (Field field : allFields) {
    if (Modifier.isPrivate(field.getModifiers())) {
        privateFields.add(field);
    }
}

    Note that getDeclaredFields() will not return inherited fields.

    Eventually, you get the type of the fields with the method Field.getType().