1. 逸出
① private对象的逸出
/**
* 描述： 发布逸出
*/
public class MultiThreadsError3 {
private Map<String, String> states;
public MultiThreadsError3() {
states = new HashMap<>();
states.put("1", "周一");
states.put("2", "周二");
states.put("3", "周三");
states.put("4", "周四");
}
public Map<String, String> getStates() {
return states;
}
public Map<String, String> getStatesImproved() {
return new HashMap<>(states);
}
public static void main(String[] args) {
MultiThreadsError3 multiThreadsError3 = new MultiThreadsError3();
Map<String, String> states = multiThreadsError3.getStates();
System.out.println(states.get("1"));
states.remove("1");
System.out.println(states.get("1"));
System.out.println(multiThreadsError3.getStatesImproved().get("1"));
multiThreadsError3.getStatesImproved().remove("1");
System.out.println(multiThreadsError3.getStatesImproved().get("1"));
}
}
② 还未完成初始化就将对象提供给外界 - 初始化未完毕，就this赋值
/**
* 描述： 初始化未完毕，就this赋值
*/
public class MultiThreadsError4 {
static Point point;
public static void main(String[] args) throws InterruptedException {
new PointMaker().start();
// Thread.sleep(10);
Thread.sleep(105);
if (point != null) {
System.out.println(point);
}
}
}
class Point {
private final int x, y;
public Point(int x, int y) throws InterruptedException {
this.x = x;
MultiThreadsError4.point = this;
Thread.sleep(100);
this.y = y;
}
@Override
public String toString() {
return x + "," + y;
}
}
class PointMaker extends Thread {
@Override
public void run() {
try {
new Point(1, 1);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
③ 还未完成初始化就将对象提供给外界 - 注册监听器
/**
* 描述： 观察者模式
*/
public class MultiThreadsError5 {
int count;
public MultiThreadsError5(MySource source) {
source.registerListener(new EventListener() {
@Override
public void onEvent(Event e) {
System.out.println("\n我得到的数字是" + count);
}
});
//do other thing
for (int i = 0; i < 10000; i++) {
System.out.print(i);
}
count = 100;
}
public static void main(String[] args) {
MySource mySource = new MySource();
new Thread(new Runnable() {
@Override
public void run() {
try {
Thread.sleep(10);
} catch (InterruptedException e) {
e.printStackTrace();
}
mySource.eventCome(new Event() {
});
}
}).start();
MultiThreadsError5 multiThreadsError5 = new MultiThreadsError5(mySource);
}
static class MySource {
private EventListener listener;
void registerListener(EventListener eventListener) {
this.listener = eventListener;
}
void eventCome(Event e) {
if (listener != null) {
listener.onEvent(e);
} else {
System.out.println("还未初始化完毕");
}
}
}
interface EventListener {
void onEvent(Event e);
}
interface Event {
}
}
④ 构造函数中运行线程
/**
* 描述： 构造函数中新建线程
*/
public class MultiThreadsError6 {
private Map<String, String> states;
public MultiThreadsError6() {
new Thread(new Runnable() {
@Override
public void run() {
states = new HashMap<>();
states.put("1", "周一");
states.put("2", "周二");
states.put("3", "周三");
states.put("4", "周四");
}
}).start();
}
public Map<String, String> getStates() {
return states;
}
public static void main(String[] args) throws InterruptedException {
MultiThreadsError6 multiThreadsError6 = new MultiThreadsError6();
Thread.sleep(1000);
System.out.println(multiThreadsError6.getStates().get("1"));
}
}
2. 如何解决逸出
① 对于private对象返回副本
② 工厂模式解决还未完成初始化就将对象提供给外界
/**
* 描述： 用工厂模式修复刚才的初始化问题
*/
public class MultiThreadsError7 {
int count;
private EventListener listener;
private MultiThreadsError7(MySource source) {
listener = new EventListener() {
@Override
public void onEvent(MultiThreadsError5.Event e) {
System.out.println("\n我得到的数字是" + count);
}
};
for (int i = 0; i < 10000; i++) {
System.out.print(i);
}
count = 100;
}
public static MultiThreadsError7 getInstance(MySource source) {
MultiThreadsError7 safeListener = new MultiThreadsError7(source);
source.registerListener(safeListener.listener);
return safeListener;
}
public static void main(String[] args) {
MySource mySource = new MySource();
new Thread(new Runnable() {
@Override
public void run() {
try {
Thread.sleep(10);
} catch (InterruptedException e) {
e.printStackTrace();
}
mySource.eventCome(new MultiThreadsError5.Event() {
});
}
}).start();
MultiThreadsError7 multiThreadsError7 = new MultiThreadsError7(mySource);
}
static class MySource {
private EventListener listener;
void registerListener(EventListener eventListener) {
this.listener = eventListener;
}
void eventCome(MultiThreadsError5.Event e) {
if (listener != null) {
listener.onEvent(e);
} else {
System.out.println("还未初始化完毕");
}
}
}
interface EventListener {
void onEvent(MultiThreadsError5.Event e);
}
interface Event {
}
}