2 * Copyright © 2019 Damyan Ivanov.
3 * This file is part of Mobile-Ledger.
4 * Mobile-Ledger is free software: you can distribute it and/or modify it
5 * under the term of the GNU General Public License as published by
6 * the Free Software Foundation, either version 3 of the License, or
7 * (at your opinion), any later version.
9 * Mobile-Ledger is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License terms for details.
14 * You should have received a copy of the GNU General Public License
15 * along with Mobile-Ledger. If not, see <https://www.gnu.org/licenses/>.
18 package net.ktnx.mobileledger.utils;
20 import java.util.Observable;
21 import java.util.Observer;
23 public class ObservableValue<T> {
24 private final ObservableValueImpl<T> impl = new ObservableValueImpl<>();
25 public ObservableValue() {}
26 public ObservableValue(T initialValue) {
27 impl.setValue(initialValue, false);
29 public void set(T newValue) {
30 impl.setValue(newValue);
33 return impl.getValue();
35 public void addObserver(Observer o) {
38 public void deleteObserver(Observer o) {
39 impl.deleteObserver(o);
41 public void notifyObservers() {
42 impl.notifyObservers();
44 public void notifyObservers(Object arg) {
45 impl.notifyObservers(arg);
47 public void deleteObservers() {
48 impl.deleteObservers();
50 public boolean hasChanged() {
51 return impl.hasChanged();
53 public int countObservers() {
54 return impl.countObservers();
56 private class ObservableValueImpl<T> extends Observable {
58 public void setValue(T newValue) {
59 setValue(newValue, true);
61 private synchronized void setValue(T newValue, boolean notify) {
62 if ((newValue == null) && (value == null)) return;
64 if ((newValue != null) && newValue.equals(value)) return;
69 if (notify) notifyObservers(oldValue);