java - 替换包含正则表达式的行

Question

我有一个包含多行的输入字符串(由\n 分隔)。我需要在行中搜索模式，如果找到，则将整行替换为空字符串。

我的代码是这样的，

Pattern p = Pattern.compile("^.*@@.*$");  
String regex = "This is the first line \n" +  
               "And this is second line\n" +  
               "Thus is @@{xyz} should not appear \n" +  
               "This is 3rd line and should come\n" +  
               "This will not appear @@{abc}\n" +  
               "But this will appear\n";  
Matcher m = p.matcher(regex);  
System.out.println("Output: "+m.group());  

我希望响应为:

Output: This is the first line       
        And this is second line  
        This is 3rd line and should come  
        But this will appear.

我无法获取它，请帮帮我。

谢谢，
阿米特

Answer 1

为了让 ^ 匹配一行的开头，而 $ 匹配一行的结尾，您需要启用多行选项。您可以通过在您的正则表达式前面添加 (?m) 来做到这一点:"(?m)^.*@@.*$"。

此外，您希望在正则表达式找到匹配项时继续分组，可以这样做:

while(m.find()) {
  System.out.println("Output: "+m.group());
}

请注意正则表达式将匹配这些行(不是您指定的行):

Thus is @@{xyz} should not appear 
This will not appear @@{abc}

但是如果你想替换包含 @@ 的行，正如你帖子的标题所暗示的那样，这样做:

public class Main { 
    public static void main(String[] args) {
        String text = "This is the first line \n" +  
                      "And this is second line\n" +  
                      "Thus is @@{xyz} should not appear \n" +  
                      "This is 3rd line and should come\n" +  
                      "This will not appear @@{abc}\n" +  
                      "But this will appear\n";  
        System.out.println(text.replaceAll("(?m)^.*@@.*$(\r?\n|\r)?", ""));
    }
}

编辑:解释了 PSeed 提到的 *nix、Windows 和 Mac 换行符。