java - 正则表达式替换 IP 地址

Question

75.122.1.23

我需要将第三个数字替换为 2，使其看起来像 75.122.2.23

什么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");

评论表单:

/^                 # 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