public void filter(String comboBoxValue, String by) {
		if (comboBoxValue.equals("") && by.equals("")) {
			refreshAvailableClasses();
		} else {
			this.isFiltered = true;

			this.filteredClassesSet = new ResourceSet();

			for (Resource resource : this.availableClassesSet) {
				Class classEntity = (Class) resource;

				// Be sure that the comboBoxValues is actually equal to what is
				// written!
				if (comboBoxValue.equals("Class No.")) {
					if (classEntity.getClassNo().contains(by)) {
						this.filteredClassesSet.add(classEntity);
					}
				} else if (comboBoxValue.equals("Class name")) {
					if (classEntity.getClassName().contains(by)) {
						this.filteredClassesSet.add(classEntity);
					}
				} else if (comboBoxValue.equals("Year")) {
					String year = classEntity.getYear() + "";
					if (year.contains(by)) {
						this.filteredClassesSet.add(classEntity);
					}
				}
				refreshAvailableClasses();
			}
		}
	}