Java 索引越界异常索引：2，大小：2答案

【问题标题】：Java index out of bounds exception index:2, Size:2Java 索引越界异常索引：2，大小：2
【发布时间】：2019-03-17 20:27:27
【问题描述】：

这是我得到的错误。如果您需要有关完整代码的更多信息，请告诉我。

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)

这是我的代码，我不明白它有什么问题 i+1 不应该越界...（不太擅长编程，所以我不太了解问题所在。）

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);

【问题讨论】：

对于大小2 的列表，当i = 1、list.get(2) 超出范围时。索引从0开始
列表（和数组）从零开始。所以一个列表的最大索引是1，而它的大小是2。
好的，谢谢。我对 .size() 感到困惑，因为它的索引不是从零开始的。谢谢。

标签： java list for-loop

【解决方案1】：

你在第一行看到错误：Index: 2, Size: 2

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

所以这里的条件是满足的，因为列表大小是2。

temp = temp + list.get(i+1); --> 这就是问题所在。

您是说：get(i+1) 等于 2，但索引实际上是 1。第一次迭代 = i+1 => 0+1 = 1 第二次迭代 = i+1 => 1+1 = 2 ---> 这是你越界的地方。

【讨论】：

【解决方案2】：

在 java 中，数组和列表从索引 0 开始，到索引 size - 1 结束。因此，如果在您的循环中是i = 1，那么list.get(i + 1) 将导致IndexOutOfBoundsException，因为您正在尝试访问不存在的索引2。

【讨论】：