Java索引超出范圍例外索引：2，大小：2

Question

這是我得到的錯誤。 如果您需要有關完整代碼的更多信息，請告訴我。

Exception in thread "AWT-EventQueue-0" java.lang.IndexOutOfBoundsException: Index: 2, Size: 2
    at java.util.ArrayList.rangeCheck(Unknown Source)
    at java.util.ArrayList.get(Unknown Source)
    at main.Field.upCountFirst(Field.java:158)
    at main.Field$1.actionPerformed(Field.java:55)
    at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
    at javax.swing.AbstractButton$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.dispatchEventImpl(Unknown Source)
    at java.awt.EventQueue.access$500(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(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)                         

這是我的代碼，我不明白它有什么問題，我不應該超出范圍（+1）（不是很擅長編程，所以我不太清楚這個問題。）

list.add(x);
String temp = x;
for(int i = 0; i<list.size(); i++) {
    System.out.println(list.get(i) + " X" + list.size());
    if(list.size() >= 2) {
        temp = temp + list.get(i+1);
    }
}
System.out.println(temp);

Answer 1

您會在錯誤的第一行看到：索引：2，大小：2

if(list.size() >= 2) {
    temp = temp + list.get(i+1);
}

因此這里滿足條件，因為列表大小為2。

temp = temp + list.get(i+1); ->這是問題所在。

您的意思是：get（i + 1）等於2，但索引實際上是1。第一次迭代= i+1 => 0+1 = 1第二次迭代= i+1 => 1+1 = 2 --->這就是您要越界的地方。

Answer 2

在java數組和列表中，從索引0開始，以索引size - 1結束。 因此，如果您的循環中i = 1則list.get(i + 1)將導致IndexOutOfBoundsException ，因為您正嘗試訪問不存在的索引2 。