简体   繁体   中英

How can I add an Map Entry to an ArrayList?

I'm creating an ArrayList of Map Entry key-value pairs. This is so I can store lots of individual words (as a key) and save the total number of times they are used (as the value).

I need to be able to sort the ArrayList by value so I can order the words by their values.

I have 2 problems:

  1. I don't know the syntax to add a map entry to the ArrayList
  2. I'm not sure how to sort the ArrayList

Any help much appreciated!

protected void addKeywords(Status status) {
    // get tweet
    String str = status.getText();
    // split into an array remove punctuation and make lower case
    String[] splited = str.replaceAll("[^a-zA-Z ]", "").toLowerCase()
            .split("\\s+");
    // vars used in loop
    String thisStr;
    int wordTot;
    Entry<String, Integer> newEntry = null;

    for (int i = 0; i < splited.length; i++) {
        // get word from array
        thisStr = splited[i].toLowerCase();
        thisStr = "hi";

        // if this is the first word to be added
        if (mapList.size() == 0) {
            //this is the syntax that I don't know!
            newEntry.key = theStr;
            newEntry.value = 1;
            mapList.add(newEntry);
        } else {
            boolean alreadyExists = false;
            //iterate through mapList
            for (Entry<String, Integer> entry : mapList) {
                // already exists
                if (entry.getKey() == thisStr) {
                    wordTot = entry.getValue();
                    //increment the value
                    wordTot++;
                    entry.setValue(wordTot);
                    break; 
                } 

            }
            //if we have reached here the value must not be in the arraylist so add it

            //again - this is the syntax that I don't know!
            newEntry.key = theStr;
            newEntry.value = 1;
            mapList.add(newEntry);
        }

    }

}

-EDIT - working code Hi, I've added the new code to add map entries to the ArrayList and that is working great.

I have also updated my sort code and this is working great too:

private void sortMap() {            
    Collections.sort(mapList, new Comparator<Map.Entry<String, Integer>>() {
          @Override
          public int compare(Map.Entry<String, Integer> o1, Map.Entry<String, Integer> o2) {
            if (o1.getValue()>o2.getValue()){
                return 1;
            }else if (o1.getValue()<o2.getValue()){
                return -1;
            }else{
                return 0;
            }
          }
        });
}
List<Map.Entry<String, String>> list = new ArrayList<Map.Entry<String, String>>();
list.add(new AbstractMap.SimpleEntry<String, String>("foo", "bar"));

Collections.sort(list, new Comparator<Map.Entry<String, String>>() {
  @Override
  public int compare(Map.Entry<String, String> o1, Map.Entry<String, String> o2) {
    return 0;
  }
});

Consider the contract of the compare method:

Compares its two arguments for order. Returns a negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater than the second.

The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.

 
粤ICP备18138465号  © 2020-2024 STACKOOM.COM