private static boolean isValidField( Field f ) {
		int modifiers = f.getModifiers();
		return (modifiers & (Modifier.FINAL|Modifier.STATIC)) == 0 && !f.isSynthetic();
	}
Applies the given value to a field of the given object.

@param obj the object
@param fieldName the name of the field
@param key the key (only used for error reporting)
@param value the new value
@return the old value of the field
@throws UnknownStyleException if object does not have a field with given name
@throws IllegalArgumentException if value type does not fit to expected type
flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatStylingSupport.java