Java的String中的subString()方法

public String substring(int beginIndex, int endIndex)

第一个int为开始的索引，对应String数字中的开始位置，

第二个是截止的索引位置，对应String中的结束位置

1、取得的字符串长度为：endIndex - beginIndex;

2、从beginIndex开始取，到endIndex结束，从0开始数，其中不包括endIndex位置的字符

如：

"hamburger".substring(4, 8) returns "urge"

 "smiles".substring(1, 5) returns "mile"

取长度大于等于3的字符串a的后三个子字符串，只需a.subString(a.length()-3, a.length());

手册中的具体说明如下：

substring

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"

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.