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. 所以应该是substring(4,6)
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.
所以应该是substring(4,6)
str.substring(int fromIndex,int endIndex)你说的...at()，指的是str.charAt(int index)吧，
它是取索引号为index的字符。