界必須積極

Question

這就是我不斷收到錯誤（這我理解，但不能因爲解決IDK的是什麼問題）

[14:25:50 ERROR]: Could not pass event BlockBreakEvent to SurgeGlowstone v1.0 
org.bukkit.event.EventException 
     at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:297) ~[custom.jar:git-PaperSpigot-a925999] 
     at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[custom.jar:git-PaperSpigot-a925999] 
     at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:513) [custom.jar:git-PaperSpigot-a925999] 
     at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:498) [custom.jar:git-PaperSpigot-a925999] 
     at net.minecraft.server.v1_7_R4.PlayerInteractManager.breakBlock(PlayerInteractManager.java:264) [custom.jar:git-PaperSpigot-a925999] 
     at net.minecraft.server.v1_7_R4.PlayerInteractManager.dig(PlayerInteractManager.java:118) [custom.jar:git-PaperSpigot-a925999] 
     at net.minecraft.server.v1_7_R4.PlayerConnection.a(PlayerConnection.java:569) [custom.jar:git-PaperSpigot-a925999] 
     at net.minecraft.server.v1_7_R4.PacketPlayInBlockDig.a(PacketPlayInBlockDig.java:41) [custom.jar:git-PaperSpigot-a925999] 
     at net.minecraft.server.v1_7_R4.PacketPlayInBlockDig.handle(PacketPlayInBlockDig.java:65) [custom.jar:git-PaperSpigot-a925999] 
     at net.minecraft.server.v1_7_R4.NetworkManager.a(NetworkManager.java:189) [custom.jar:git-PaperSpigot-a925999] 
     at net.minecraft.server.v1_7_R4.ServerConnection.c(ServerConnection.java:103) [custom.jar:git-PaperSpigot-a925999] 
     at net.minecraft.server.v1_7_R4.MinecraftServer.v(MinecraftServer.java:801) [custom.jar:git-PaperSpigot-a925999] 
     at net.minecraft.server.v1_7_R4.DedicatedServer.v(DedicatedServer.java:286) [custom.jar:git-PaperSpigot-a925999] 
     at net.minecraft.server.v1_7_R4.MinecraftServer.u(MinecraftServer.java:651) [custom.jar:git-PaperSpigot-a925999] 
     at net.minecraft.server.v1_7_R4.MinecraftServer.run(MinecraftServer.java:557) [custom.jar:git-PaperSpigot-a925999] 
     at net.minecraft.server.v1_7_R4.ThreadServerApplication.run(SourceFile:628) [custom.jar:git-PaperSpigot-a925999] 
Caused by: java.lang.IllegalArgumentException: bound must be positive 
     at java.util.Random.nextInt(Random.java:388) ~[?:1.8.0_131] 
     at com.surgehcf.listeners.PlayerListener.onBreak(PlayerListener.java:49) ~[?:?] 
     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_131] 
     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_131] 
     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_131] 

這裏是我的代碼：

public static int randInt(int min, int max) { 

    // NOTE: This will (intentionally) not run as written so that folks 
    // copy-pasting have to think about how to initialize their 
    // Random instance. Initialization of the Random instance is outside 
    // the main scope of the question, but some decent options are to have 
    // a field that is initialized once and then re-used as needed or to 
    // use ThreadLocalRandom (if using at least Java 1.7). 
    Random rand = new Random(); 

    // nextInt is normally exclusive of the top value, 
    // so add 1 to make it inclusive 
    int randomNum = rand.nextInt((max - min) + 1) + min; 

    return randomNum; 
} 
@EventHandler 
public void onBreak(BlockBreakEvent e) { 
    Player p = e.getPlayer(); 
    Block b = e.getBlock(); 
    JsonBox bx = GlowstoneMountain.getInstance().getRegionAqui(b.getLocation()); 
    if (bx != null && b.getType() == Material.GLOWSTONE && b.getWorld().getName().equalsIgnoreCase("world_nether")) { 
     b.getWorld().dropItemNaturally(b.getLocation(), new ItemStack(Material.GLOWSTONE_DUST,randInt(4,2))); 
    } 
} 

我總是做一個在4和2之間的隨機數，但stil它說的減去基本上我想要的是一個int在2和4之間以獲得隨機輸出

Answer 1

理解的錯誤（和如何解決它），檢查Java docs on Random's nextInt()：

參數：

bound - the upper bound (exclusive). Must be positive.

拋出：

IllegalArgumentException - if bound is not positive

然而，randInt(4,2)，正如你所說的你的方法，恰恰是錯誤的方式。它使用4作爲min,2作爲max，因此最終得到一個負界限（-1），導致異常。

因此，我建議如下修改你的方法：

public static int randInt(int a, int b) { 
    int min = Math.min(a, b); 
    int max = Math.max(a, b); 
    return rand.nextInt((max - min) + 1) + min; 
} 

說明：

現在，你信任你的函數的用戶尊重的參數（min, max訂單 - 不max, min ）。雖然你可以做到這一點，但你只是經歷過多快會讓你陷入麻煩，即使用戶是你。

因此，添加類似上述的安全措施將導致更健壯的代碼。在這裏，我們只檢查兩個值中的哪一個是smaller，哪一個是bigger，然後相應地使用它們。

當然，您也可以將您的方法保持不變，只需將呼叫更改爲randInt(2,4)即可。

注：

它仍然有可能爲用戶獲取方法打破（拋出一個異常，如上），但我會離開它作爲一個練習，你要弄清楚如何 - 和你如何防範它。 :-)

Answer 2

在onBreak方法中，在if語句中，更改此：

new ItemStack(Material.GLOWSTONE_DUST,randInt(4,2))); 

這樣：

new ItemStack(Material.GLOWSTONE_DUST,randInt(2,4))); 

現在你正在試圖獲得爲2的最高分和4分鐘一那是不可能的隨機int值。將其更改爲最大值4和最小值2。

randInt函數的參數順序爲（min，max）。目前你對待它，喜歡它的（最大，最小）