索引越界如何解决？

[GAODBK]

public static final int OFF_SET_DEFAULT = 2;

设置OFF_SET_DEFAULT=2，将组件滚动到最后一个，出现报错：
java.lang.IndexOutOfBoundsException: Index 18 out of bounds for length 17

能不能帮忙提供思路

Set OFF_SET_DEFAULT=2 and scroll the component to the last one, and an error message appears
java.lang.IndexOutOfBoundsException: Index 18 out of bounds for length 17

Can you help with ideas