Question

我有一个很长的文本文件。

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，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

我需要从副本中获取第一行，其他行将被忽略。

我试过了：

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();
    }
}

这是有效的，但只有在整行重复时才会删除。

如何更改它以便它在每行中查找第一个单词并在此检查重复项;如果没有找到重复，保存完整的行;如果重复则忽略该行？

Answer 1

您需要维护Set<String>，只保留每行的第一个单词。

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

我会写关于添加到列表的部分使用HashMap

    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);
        }
    }

所以循环将只添加uinuque行，使用第一个单词作为键

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();

                    }
                }

Java从字符串数组[0]的文件搜索中删除重复项

3 个答案: