Java 帮助 - StringIndexOutOfBoundsException - 字符串索引超出范围 : -1

Question

我的一些代码遇到了问题，我真的无法解决这个错误。

我正在使用 Interprolog(Java+Prolog) 请参阅 here

这是堆栈跟踪:

  Exception in thread "AWT-EventQueue-0" java.lang.StringIndexOutOfBoundsException: String index out of range: -1
    at java.lang.String.substring(Unknown Source)
    at      com.declarativa.interprolog.AbstractPrologEngine.copyToTemp(AbstractPrologEngine.java)
 at com.declarativa.interprolog.AbstractPrologEngine.consultFromPackage(AbstractPrologEngine.java)
 at LoginHandler.actionPerformed(LoginHandler.java:24)
 at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
 at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
 at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
 at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
 at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
 at java.awt.Component.processMouseEvent(Unknown Source)
 at javax.swing.JComponent.processMouseEvent(Unknown Source)
 at java.awt.Component.processEvent(Unknown Source)
 at java.awt.Container.processEvent(Unknown Source)
 at java.awt.Component.dispatchEventImpl(Unknown Source)
 at java.awt.Container.dispatchEventImpl(Unknown Source)
 at java.awt.Component.dispatchEvent(Unknown Source)
 at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
 at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
 at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
 at java.awt.Container.dispatchEventImpl(Unknown Source)
 at java.awt.Window.dispatchEventImpl(Unknown Source)
 at java.awt.Component.dispatchEvent(Unknown Source)
 at java.awt.EventQueue.dispatchEvent(Unknown Source)
 at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
 at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
 at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
 at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
 at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
 at java.awt.EventDispatchThread.run(Unknown Source)

以及有问题的代码:

      myEngine = new NativeEngine();
  myEngine.consultFromPackage("C:\\interprolog212a\\userlist.p", LoginHandler.class);
  boolean x = myEngine.deterministicGoal("hasAccess(user,pass)");

有什么想法吗？我碰壁了...

哦，第 24 行是我发布的第二行代码。

编辑:userlist.p的内容:

hasAccess(tom,123).
hasAccess(bob,456).

根据下面的一些建议，我将 loginhandler 和相关类移至它们自己的包中，并将 userlist.p 移至该包中，现在我收到此错误:

com.declarativa.interprolog.util.IPException: Problem consulting from package         archive:C:\Users\Keval\AppData\Local\Temp\IP_5283895338735856757\userlist.p

Answer 1

我认为开源是好的。它正在这样做:

String className = rc.getName();    
String packageName = className.substring(0,className.lastIndexOf('.'));

rc 是您的调用类。所以我想您的 LoginHandler 类位于默认包中，这会导致此代码出错吗？尝试将其放入包中，即将 package blah; 添加到其顶部并将其移动到具有该名称的目录。

它这样做是因为它假设 userlist.pl 实际上与您的代码位于同一位置，并且它尝试使用包名称来查找加载代码的位置。我认为您不能按照您实际尝试的方式使用 consultFromPackage() ，因为它应该只能解析文件名，而不是完整的路径。

哦，你可以获得来源。它位于 zip file链接自 the website .