关于String.substring方法
关于String.substring方法

该方法的签名为

String substring(int beginIndex,?int endIndex)

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结合javadoc和源代码，对该方法进行分析：

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根据beginIndex与0或count的比较、beginIndex与endIndex的比较、endIndex与字符串长度count的比较，有几种情况：

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#beginIndex与0比较beginIndex与endIndex比较endIndex与count比较结果1<0IndexOutOfBoundsException2=0<<子串3<=String对象本身4<>IndexOutOfBoundsException5="" ?空串6
>IndexOutOfBoundsException7>0 & <count<<子串8<=子串9<>IndexOutOfBoundsException10="" 空串11>IndexOutOfBoundsException12=count<IndexOutOfBoundsException13="" 空串14>IndexOutOfBoundsException15>countIndexOutOfBoundsException

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上面的表格列出的情况多达15种，可见要对代码进行覆盖性测试确实是非常困难的。

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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.

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public String substring(int?beginIndex,                        int?endIndex)

Returns a new string that is a substring of this string. The substring begins at the specified beginIndex and extends to the character at index endIndex - 1. Thus the length of the substring is endIndex-beginIndex.

Examples:

 "hamburger".substring(4, 8) returns "urge" "smiles".substring(1, 5) returns "mile" 

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

PS：iteye的表格编辑实在很困难，望高人指点。

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