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划分).我需要在行中搜索一个模式,如果找到它,则用空字符串替换整行.

我的代码看起来像这样,

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());  

我希望回复如下:

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

我无法得到它,请帮帮我.

谢谢,
阿米特

Answer 1

为了使^匹配成为行的开头并$匹配行的结尾,您需要启用多行选项.你可以通过(?m)在你的正则表达式前添加如下:"(?m)^.*@@.*$".

此外,您希望在正则表达式找到匹配时保持分组,这可以这样做:

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

请注意,正则表达式将匹配这些行(而不是您指定的行):

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

但是如果你想要替换包含的行@@,就像你帖子的标题所暗示的那样,那样做:

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:占PSeed提到的*nix,Windows和Mac换行符.