String.replace() 不替换所有出现

Question

我有一个很长的字符串，看起来与此类似。

355,356,357,358,359,360,361,382,363,364,365,366,360,361,363,366,360,361,363,366,360,361,363,366,360,361,363,366,360,361,363,366,360,361,363,366,360,361,363,366,368,369,313,370,371,372,373,374,375,376,377,378,379,380,381,382,382,382,382,382,382,383,384,385,380,381,382,382,382,382,382,386,387,388,389,380,381,382,382,382,382,382,382,390,391,380,381,382,382,382,382,382,392,393,394,395,396,397,398,399,....

当我尝试使用以下代码从字符串中删除数字 382 时。

String str = "355,356,357,358,359,360,361,382,363,364,365,366,360,361,363,366,360,361,363,366,360,361,363,366,360,361,363,366,360,361,363,366,360,361,363,366,360,361,363,366,368,369,313,370,371,372,373,374,375,376,377,378,379,380,381,382,382,382,382,382,382,383,384,385,380,381,382,382,382,382,382,386,387,388,389,380,381,382,382,382,382,382,382,390,391,380,381,382,382,382,382,382,392,393,394,395,396,397,398,399,...."
str = str.replace(",382,", ",");

但似乎并非所有事件都被替换。 原来出现次数超过 3000 次的字符串在替换后仍然出现了大约 630 次。

String.replace() 的能力是否有限？ 如果是这样，是否有可能实现我需要的方法？

Answer 1

我认为问题是你的第一个参数replace() ，特别是382之前和之后的逗号（，）。如果你有“382,382,383”，你将只匹配内部“，382”，并留下最初的一个。 尝试：

str.replace("382,", "");

虽然在最后它将无法匹配“382”，因为它之后没有逗号。

完整的解决方案可能需要两个方法调用：

str = str.replace("382", "");  // Remove all instances of 382
str.replaceAll(",,+", ",");    // Compress all duplicates, triplicates, etc. of commas

这结合了两种方法：

str.replaceAll("382,?", "");  // Remove 382 and an optional comma after it. 

注意：如果382在结尾，则后两种方法都会留下尾随逗号。

Answer 2

您还需要替换尾随逗号（如果存在，如果列表中的最后一个则不会）：

str = str.replaceAll("\\b382,?", "");

注意\\b字边界以防止匹配"-,1382,-" 。

以上将转换：

382,111,382,1382,222,382

至：

111,1382,222

Answer 3

尝试这个

str = str.replaceAll(",382,", ",");

Answer 4

首先，删除匹配字符串中的前一个逗号。 然后，通过使用java正则表达式将逗号替换为单个逗号来删除重复的逗号。

 String input = "355,356,357,358,359,360,361,382,363,364,365,366,360,361,363,366,360,361,363,366,360,361,363,366,360,361,363,366,360,361,363,366,360,361,363,366,360,361,363,366,368,369,313,370,371,372,373,374,375,376,377,378,379,380,381,382,382,382,382,382,382,383,384,385,380,381,382,382,382,382,382,386,387,388,389,380,381,382,382,382,382,382,382,390,391,380,381,382,382,382,382,382,392,393,394,395,396,397,398,399";
    String result = input.replace("382,", ","); // remove the preceding comma
    String result2 = result.replaceAll("[,]+", ","); // replace duplicate commas

    System.out.println(result2);

Answer 5

正如戴夫已经说过的，问题是你的模式重叠了。 在字符串"...,382,382,..."有两次出现",382," ：

"...,382,382,..."
    -----         first occurrence
        -----     second occurrence

这两个匹配项在逗号处重叠，因此Java只能替换其中一个。 当找到事件时，它还没有看到你用什么替换模式，因此当替换第一个匹配项被逗号替换时",382,"它不会看到新的",382,"出现。

如果您的数据已知不包含超过3位数的数字，那么您可能会：

str.replace("382,", "");

然后作为特例处理最后的事件。 但是如果你的数据可以包含大数字，那么"...,1382,..."将被"...,1,..."取代"...,1,..."这可能不是你想要的。

以下是两个没有上述问题的解决方案：

首先，只需重复更换，直到不再发生变化：

String oldString = str;
str = str.replace(",382,", ",");
while (!str.equals(oldString)) {
    oldString = str;
    str = str.replace(",382,", ",");
}

之后，您将必须处理字符串末尾可能出现的事件。

其次，如果你有Java 8，你可以自己做更多的工作并使用Java流：

str = Arrays.stream(str.split(","))
    .filter(s -> !s.equals("382"))
    .collect(Collectors.joining(","));

这首先将字符串拆分为“，”，然后过滤掉所有等于“382”的字符串，然后将剩余的字符串再次与“，”之间连接起来。

（两个代码段都未经过测试。）

Answer 6

传统方式：

    String str = ",abc,null,null,0,0,7,8,9,10,11,12,13,14";
    String newStr = "", word = "";
    for (int i=0; i<str.length(); i++) {
        if (str.charAt(i) == ',') {
            if (word.equals("null") || word.equals("0"))
                word = "";
            newStr += word+",";
            word = "";
        } else {
            word += str.charAt(i);
            if (i == str.length()-1)
                newStr += word;
        }
    }
    System.out.println(newStr);

输出：,abc,,,,,7,8,9,10,11,12,13,14