Java String索引越界混乱

Question

Suppose I have a

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

Why?

Answer 1

The Javadocs for this method state:

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.

An end index of length is ok, but length + 1 is not.

Answer 2

According to docs :

public String substring(int beginIndex, int endIndex)

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

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

Since System.out.println(temp.substring(0,5)); where 5 > length of string ( abcd ), hence the exception.

Answer 3

因为子字符串以endIndex-1结尾。

Answer 4

substring（0,4）不考虑0到4。它考虑0到3。第二个索引始终减去1。在第二种情况下，temp [4]超出范围。