当索引1中没有元素时，为什么不跟随java代码抛出java.lang.StringIndexOutOfBoundsException？ [英] Why doesn't following java code throw java.lang.StringIndexOutOfBoundsException when there is no element present at index 1?

问题描述

String str="x";
System.out.println(str.substring(1));

来自Javadoc：

String java.lang.String.substring（int beginIndex）：返回一个新字符串，该字符串是此字符串的子字符串。 子字符串以指定索引处的字符开头，并延伸到此字符串的末尾。

String java.lang.String.substring(int beginIndex): Returns a new string that is a substring of this string. The substring begins with the character at the specified index and extends to the end of this string.

推荐答案

看一下 JavaDoc ，并特别注意空虚示例：

Take a look at the JavaDoc, and pay specific attention to the "emptiness" example:

Returns a string that is a substring of this string. The substring begins
with the character at the specified index and extends to the end of
this string. 

Examples: 

 "unhappy".substring(2) returns "happy"
 "Harbison".substring(3) returns "bison"
 "emptiness".substring(9) returns "" (an empty string)

Parameters:
beginIndex the beginning index, inclusive.
Returns:
the specified substring.
Throws:
IndexOutOfBoundsException - if beginIndex is negative or larger than
                            the length of this String object

如果beginIndex为负或大于此String对象的长度，则抛出异常 ;在您的情况下，beginIndex等于字符串的长度，而不是更大。

An exception is throw if beginIndex is negative or larger than the length of this String object; in your case, beginIndex is equal to the length of your string, and not larger.

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