title: Counting the number of common elements between two arraylists - Java
body: <p>I'm trying to see how many common elements two array lists have. This is the code I've come up with but this unfortunately returns: Exception in thread "AWT-EventQueue-0" </p>
  
  <p>Here is the code:</p>
  
  <pre><code>private int score(int correctAnswers){ 
      correctAnswers = 0;
  
      Collections.addAll(quiz1Answers, "ottawa", "toronto", "tokyo", "northamerica", "seoul", "Asia", "unitedstates", "50");
      Collections.addAll(quiz1UserAnswers, "ottawa", "dfdf", "tokyo", "northamerica", "seoul", "x", "unitedstates", "50");
  
      for (int i = 0; i &lt;= quiz1Answers.size(); i++)
      {
          if (quiz1Answers.contains(quiz1UserAnswers.get(i)))
          {
              correctAnswers++;
  
          }
      } 
      return correctAnswers;
  }
  </code></pre>
  
  <p>How would I go about solving this?</p>
  
  <p>EDIT: Here is the full error messsage:</p>
  
  <pre><code>Exception in thread "AWT-EventQueue-0" java.lang.IndexOutOfBoundsException: Index: 8, Size: 8
  at java.util.ArrayList.rangeCheck(ArrayList.java:635)
  at java.util.ArrayList.get(ArrayList.java:411)
  at Quiz1.score(Quiz1.java:309)
  at Quiz1.jButton4ActionPerformed(Quiz1.java:364)
  at Quiz1.access$400(Quiz1.java:16)
  at Quiz1$5.actionPerformed(Quiz1.java:148)
  at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
  at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
  at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
  at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
  at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
  at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:289)
  at java.awt.Component.processMouseEvent(Component.java:6505)
  at javax.swing.JComponent.processMouseEvent(JComponent.java:3320)
  at java.awt.Component.processEvent(Component.java:6270)
  at java.awt.Container.processEvent(Container.java:2229)
  at java.awt.Component.dispatchEventImpl(Component.java:4861)
  at java.awt.Container.dispatchEventImpl(Container.java:2287)
  at java.awt.Component.dispatchEvent(Component.java:4687)
  at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
  at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
  at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
  at java.awt.Container.dispatchEventImpl(Container.java:2273)
  at java.awt.Window.dispatchEventImpl(Window.java:2719)
  at java.awt.Component.dispatchEvent(Component.java:4687)
  at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:735)
  at java.awt.EventQueue.access$200(EventQueue.java:103)
  at java.awt.EventQueue$3.run(EventQueue.java:694)
  at java.awt.EventQueue$3.run(EventQueue.java:692)
  at java.security.AccessController.doPrivileged(Native Method)
  at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
  at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
  at java.awt.EventQueue$4.run(EventQueue.java:708)
  at java.awt.EventQueue$4.run(EventQueue.java:706)
  at java.security.AccessController.doPrivileged(Native Method)
  at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
  at java.awt.EventQueue.dispatchEvent(EventQueue.java:705)
  at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
  at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
  at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
  at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
  at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
  at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)
  </code></pre>