如何在从方法创建的类之间共享变量？

Question

我正在为Minecraft创建一个插口插件，允许玩家使用某个命令追捕另一个玩家。

从现在开始，所有的变量都在类的顶部声明，这样它们就可以从onCommand方法中访问。但是，如果我这样做，插件将只适用于一个玩家，因为每个人的变量都是一样的，并且被每个使用命令的人覆盖（例如，所有玩家都将在命令上有一个冷却计时器，因为第一个玩家使用它）。我希望所有的变量都在onCommand方法中声明，这样变量的值对于使用命令的每个玩家来说都是唯一的。但是，如果我将它们移动到onCommand方法的顶部，我将无法再使用它们并获得以下错误（参见图片）：

• 变量“X”从内部类中访问，需要是final或有效final
• 变量“X”可能尚未初始化

我还希望一些变量是公共的，这样就可以在另一个类中使用，但似乎不允许变量在方法内部是公共的（见图）：

• 此处不允许修饰符“public”

有人能帮我解决这三个问题吗？

下面的完整代码：

package com.krekkie.hunt.commands;

import org.bukkit.Bukkit;
import org.bukkit.Location;
import org.bukkit.World;
import org.bukkit.command.Command;
import org.bukkit.command.CommandExecutor;
import org.bukkit.command.CommandSender;
import org.bukkit.entity.Player;

import java.text.MessageFormat;
import java.util.Timer;
import java.util.TimerTask;

public class HuntCommands implements CommandExecutor {

    @Override
    public boolean onCommand(CommandSender sender, Command command, String label, String[] arguments) {
        if (!(sender instanceof Player)) {
            sender.sendMessage("Only players can use that command!");
            return true;
        }
        Player player = (Player) sender;
        String playerName = player.getName();
        public Player targetPlayer;
        String targetPlayerName;
        World world = player.getWorld();
        long currentTime = world.getFullTime();

        Timer timer;
        public boolean isHunting = false;
        long fixedCooldownTime = 5*1000;
        long cooldownTime = 0;
        float cooldownTimeLeft;
        long huntStartTime = 0;

        // /hunt <player>
        if (command.getName().equalsIgnoreCase("hunt")) {
            if (!isHunting) {
                if (currentTime >= huntStartTime + cooldownTime) {
                    if (arguments.length == 1) {
                        targetPlayer = Bukkit.getPlayer(arguments[0]);
                        targetPlayerName = targetPlayer.getName();
                        try {
                            huntStartTime = world.getFullTime();
                            targetPlayer.sendMessage(MessageFormat.format("You are being hunted by {0}!", playerName));

                            timer = new Timer();
                            TimerTask timerTask = new TimerTask() {
                                int count = 0;

                                @Override
                                public void run() {
                                    Location targetPlayerLocation = targetPlayer.getLocation();
                                    float axisX = targetPlayerLocation.getBlockX();
                                    float axisY = targetPlayerLocation.getBlockY();
                                    float axisZ = targetPlayerLocation.getBlockZ();
                                    player.sendMessage(MessageFormat.format("You smell {0} at {1} {2} {3}", targetPlayerName, axisX, axisY, axisZ));

                                    count++;
                                    if (count >= 3) {
                                        timer.cancel();
                                        cooldownTime = fixedCooldownTime;
                                        player.sendMessage(MessageFormat.format("You cannot smell {0} anymore!", targetPlayerName));
                                        targetPlayer.sendMessage(MessageFormat.format("{0} lost your trace!", playerName));
                                        isHunting = false;
                                    }
                                }
                            };
                            timer.schedule(timerTask, 0, 10*1000);
                            isHunting = true;
                        } catch (IllegalArgumentException e) {
                            player.sendMessage("§c§l(!) §cInvalid argument!");
                        }
                    } else {
                        player.sendMessage("§c§l(!) §c/hunt <player>");
                    }
                } else {
                    cooldownTimeLeft = (float) Math.ceil(((huntStartTime + cooldownTime) - currentTime) / 1000);
                    player.sendMessage(MessageFormat.format("§c§l(!) §cYou need to wait {0} more minutes!", cooldownTimeLeft));
                }
            } else {
                player.sendMessage("§c§l(!) §cYou are already hunting someone!");
            }
        }

        // /huntstop
        if (command.getName().equalsIgnoreCase("huntstop")) {
            if (isHunting) {
                timer.cancel();
                cooldownTime = fixedCooldownTime;
                player.sendMessage(MessageFormat.format("You cannot smell {0} anymore!", targetPlayerName));
                targetPlayer.sendMessage(MessageFormat.format("{0} lost your trace!", playerName));
                isHunting = false;
            } else {
                player.sendMessage(("You are not hunting anyone!"));
            }
        }

        return true;
    }
}

Answer 1

您可以创建包含静态字段的助手类。这可以简单地由两个类同时共享。小心这样的“黑客”。创建这样的意大利式代码真的很容易。此外，由于每个线程都可以随时更改这样一个全局公共变量，因此多线程将变得困难。

public classA {
    ....
    Helper.setInt(42);
    ....
} 

public classB {
    ....
    Helper.getInt(); // will return 42 if the call in classA was done before 
    ....
} 


public class Helper {
    public static int someInt = 0;

    public static int getInt() {
        return someInt;
    };

    public static void setInt(int value) {
        someInt = value;
    };
}