Java从文件搜索中删除字符串数组[0]的重复项

Question

我的文本文件很长。

现在，我将从文件中删除重复项。 问题是搜索参数是列表中的第一个单词，并用“：”分隔

例如：

文件行：

11234567:229283:29833204:2394803
11234567:4577546765:655776:564456456
43523:455543:54335434:53445
11234567:43455:544354:5443

现在我将在这里：

11234567:229283:29833204:2394803
43523:455543:54335434:53445

我需要从重复项中获取第一行，其他将被忽略。

我尝试了这个：

Set<String> lines11;
try (BufferedReader reader11 = new BufferedReader(new FileReader("test.txt"))) {
    lines11 = new HashSet<>(10000); // maybe should be bigger
    String line11;
    while ((line11 = reader11.readLine()) != null) {
        lines11.add(line11);
    }
} // maybe should be bigger
try (BufferedWriter writer11 = new BufferedWriter(new FileWriter("test.txt"))) {
    for (String unique : lines11) {
        writer11.write(unique);
        writer11.newLine();
    }
}

那是可行的，但是仅当复制完整行时才删除。

我该如何更改它，以便它在每一行中查找第一个单词并在此处检查重复项； 如果没有发现重复，则保存完整的行； 如果重复则忽略该行？

Answer 1

您需要维护一个Set<String> ，仅保存每行的第一个单词。

List<String> lines11;
Set<String> dups;
try (BufferedReader reader11 = new BufferedReader(new FileReader("test.txt"))) {
    lines11 = new ArrayList<>();
    dups = new HashSet<>();
    String line11;
    while ((line11 = reader11.readLine()) != null) {
        String first = line11.split(":")[0]; // assuming your separator is :
        if (!dups.contains(first)) {
            lines11.add(line11);
            dups.add(first);
        }
    }
}
try (BufferedWriter writer11 = new BufferedWriter(new FileWriter("test.txt"))) {
    for (String unique : lines11) {
        writer11.write(unique);
        writer11.newLine();
    }
}

Answer 2

我将撰写有关使用HashMap添加到列表的部分

    String tmp[] = null;
    HashMap<String, String> lines = new HashMap<String, String>();
    String line11 = "";

    while ((line11 = reader11.readLine()) != null) {
        tmp = line11.split(":");
        if(!lines.containsKey(tmp[0])){
            lines.put(tmp[0], line11);
        }
    }

因此循环将只添加第一个单词作为键的唯一行

Answer 3

    You can add the data in list and take one more set in which you will add first word in that set and try add every time first of new line if it is in set, then it will not be added and return false. On that basis you can add data in list or directly in you new bufferreader.


List<String> lines11;
     Set<String> uniqueRecords;
                try (BufferedReader reader11 = new BufferedReader(new FileReader("test.txt"))) {
                    lines11 = new ArrayList<>(); // no need to give size it will increase dynamically
    uniqueRecords = new HashSet<>();
                    String line11;
                    while ((line11 = reader11.readLine()) != null) {
                           String firstWord = line11.substring(0, firstWord.firstIndexOf(" "));
                           if(uniqueRecords.add(firstWord )){
                               lines11.add(line11);
                                  }



                    }
                } // maybe should be bigger
                try (BufferedWriter writer11 = new BufferedWriter(new FileWriter("test.txt"))) {
                    for (String unique : lines11) {
                        writer11.write(unique);
                        writer11.newLine();

                    }
                }