正则表达式替换IP地址

Question

75.122.1.23

我需要用2代替第三个数字，所以它看起来像75.122.2.23

正则表达式可以匹配第三部分？

Answer 1

int replacementNumber = 2;
ip = ip.replaceAll("(\\d{1,3})\\.(\\d{1,3})\\.(\\d{1,3})\\.(\\d{1,3})", "$1.$2."+replacementNumber+".$4");

评论表：

/^                 # match beginning
    (
        \d{1,3}    # one address segment
        \.         # separation dot
        \d{1,3})   # second address segment
    \.             # separation dot
    \d{1,3}        # address segment to be replaced
    \.             # separation dot
    (\d{1,3})      # last address segment
$/x                # match end, ignore comments

Answer 2

^([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.
([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.([01]?\\d\\d?|2[0-4]\\d|25[0-5])$