如何在java中创建和更新字典?

Question

我正在尝试创建一个"信使"对于一个不和谐的Java机器人。我正在做这个项目来帮助我学习java。我正在初始化连接到事件侦听器的公共方法中的哈希表。我不想每次有事件发生时都重置它。这是我当前的代码:

public class botListeners extends ListenerAdapter {
@Override
public void onMessageReceived(@NotNull MessageReceivedEvent event) {
super.onMessageReceived(event);
// ISSUE HERE 
Hashtable<String, Integer> messangerDict = new Hashtable<String, Integer>();
if (!event.getAuthor().isBot()) {
String message = event.getMessage().getContentRaw();
System.out.println("A message has been sent: " + message);

String messenger = event.getAuthor().getAsTag();
if (messangerDict.containsKey(event.getAuthor().getAsTag())){
messangerDict.put(messenger, messangerDict.get(messenger) + 1);
}else {
messangerDict.put(event.getAuthor().getAsTag(), 1);
}
System.out.println(messangerDict.toString());
}
}
}

我的当前输出，每次我向"公会"写一条消息时是这样的:

A message has been sent: as
{USERTAG=1}
A message has been sent: s
{USERTAG=1}

我希望它每次递增，即第二次应该是2，而不是1。

Answer 1

每次方法执行时都创建一个新的HashTable，因此每次方法退出时，您的HashTable就消失了。将其创建为类的一个字段，如下所示:

public class botListeners extends ListenerAdapter {
Hashtable<String, Integer> messangerDict = new Hashtable<String, Integer>();
@Override
public void onMessageReceived(@NotNull MessageReceivedEvent event) {
super.onMessageReceived(event);
if (!event.getAuthor().isBot()) {
// ...