How do I take a compressed file (through indexes) and re-create the original file? (Java)

问题

Background of question

I have been developing some code that focuses on firstly, reading a string and creating a file. Secondly, spliting a string into an array. Then getting the indexes for each word in the array and finally, removing the duplicates and printing it to a different file. I currently have made the code for this here is a link https://pastebin.com/gqWH0x0 (there is a menu system as well) but it is rather long so I have refrained from implementing it in this question.

The compression method is done via hashmaps, getting indexes of the array and mapping them to the relevant word. Here is an example:

Original: "sea sea see sea see see"

Output: see[2, 4, 5],sea[0, 1, 3],

Question

The next stage is getting the output back into the original state. I am currently relatively new to java so I am not aware of the techniques required. The code should be able to take the output file (shown above) and put it back into the original.

My current thinking is that you would just rewrite this hashmap (below). Would I be correct in thinking this? I thought I should check with stack overflow first!

Map<String, Set<Integer>> seaMap = new HashMap<>(); //new hashmap
                    for (int seaInt = 0; seaInt < sealist.length; seaInt++) {
                        if (seaMap.keySet().contains(sealist[seaInt])) {
                            Set<Integer> index = seaMap.get(sealist[seaInt]);
                            index.add(seaInt);
                        } else {
                            Set<Integer> index = new HashSet<>();
                            index.add(seaInt);
                            seaMap.put(sealist[seaInt], index);
                        }                
                    }
                    System.out.print("Compressed: ");
                    seaMap.forEach((seawords, seavalues) -> System.out.print(seawords + seavalues + ","));
                    System.out.println("\n");

If anyone has any good ideas / answers then please let me know, I am really desperate for a solution!

Link to current code: https://pastebin.com/gqWH0x0K

回答1:

first you will have to separate the words with index(es) from your compressed line, using your example:

"see[2, 4, 5],sea[0, 1, 3],"

to obtain following Strings:

"see[2, 4, 5]" and "sea[0, 1, 3]"

for each you must read the indexes, e.g. for first:

2, 4 and 5

now just write the word in an ArrayList (or array) at the given index.

For the first two steps you can use a regular expression to find each word and the index list. Then use String.split and Integer.parseInt to get all indexes.

Pattern pattern = Pattern.compile("(.*?)\\[(.*?)\\],");
String line = "see[2, 4, 5],sea[0, 1, 3],";
Matcher matcher = pattern.matcher(line);
while (matcher.find()) {
    String word = matcher.group(1);
    String[] indexes = matcher.group(2).split(", ");
    for (String str : indexes) {
        int index = Integer.parseInt(str);

Now just check that the result List is big enough and set the word at the found indexes.

来源：https://stackoverflow.com/questions/43099918/how-do-i-take-a-compressed-file-through-indexes-and-re-create-the-original-fil

标签

java

hashmap

compression

hashtable