Java字符串索引越界困惑

Question

假设我有一个

String temp = "abcd";

System.out.println(temp.substring(0,4)); // out of bound, no error
System.out.println(temp.substring(0,5)); // out of bound, error

为什么？

Answer 1

Javadocs for this method状态:

The substring begins at the specified beginIndex and extends to the character at index endIndex - 1.

Throws:

IndexOutOfBoundsException - if the beginIndex is negative, or endIndex is larger than the length of this String object, or beginIndex is larger than endIndex.

length 的结束索引是可以的，但 length + 1 则不行。