What is the difference between getFields and getDeclaredFields in Java reflection

Question

I\'m a little confused about the difference between the getFields method and the getDeclaredFields method when using Java reflection.

I re

Answer 1

As already mentioned, Class.getDeclaredField(String) only looks at the fields from the Class in which you call it.

If you want to search a Field in the Class hierarchy, you can use this simple function:

/**
 * Returns the first {@link Field} in the hierarchy for the specified name
 */
public static Field getField(Class clazz, String name) {
    Field field = null;
    while (clazz != null && field == null) {
        try {
            field = clazz.getDeclaredField(name);
        } catch (Exception e) {
        }
        clazz = clazz.getSuperclass();
    }
    return field;
}

This is useful to find a private field from a superclass, for example. Also, if you want to modify its value, you can use it like this:

/**
 * Sets {@code value} to the first {@link Field} in the {@code object} hierarchy, for the specified name
 */
public static void setField(Object object, String fieldName, Object value) throws Exception {
    Field field = getField(object.getClass(), fieldName);
    field.setAccessible(true);
    field.set(object, value);
}