如何从地图特定数据中的文本文件读取？

Question

I need the read from the data file of the form:

1,14.23,1.71,2.43,15.6,127,2.8,3.06,.28,2.29,5.64,1.04,3.92,1065 2,12.72,1.81,2.2,18.8,86,2.2,2.53,.26,1.77,3.9,1.16,3.14,714 2,12.08,1.13,2.51,24,78,2,1.58,.4,1.4,2.2,1.31,2.72,630 .................................... 3,13.11,1.9,2.75,25.5,116,2.2,1.28,.26,1.56,7.1,.61,1.33,425 3,13.23,3.3,2.28,18.5,98,1.8,.83,.61,1.87,10.52,.56,1.51,675 ................and so on

Where first symbol - the key, the rest are values.

I try to do it this way

 Map<String, String> map = new HashMap<String, String>();
            BufferedReader in = new BufferedReader(new FileReader("wine.data.txt"));
            String line = "";
            while ((line = in.readLine()) != null) {
                String parts[] = line.split(",");
                for(int i = 1; i < parts.length; i++)
                map.put(parts[0], parts[i]);
                System.out.println(map.toString());
            }
            in.close();

But I see only last number of each line. How to fix it?

Answer 1

Everytime put is called, the value for the speficied key is being replaced.

You want to store the result in a Map<String, List<String>> :

String parts[] = line.split(",");
List<String> values = map.get(parts[0]);
if(values == null) {   // first time this key is found -> create new list
    values = new ArrayList<>();
    map.put(parts[0], values);
}
for(int i = 1; i < parts.length; i++) {
    values.add(parts[i]);
}

Answer 2

map associates each key with a string; each time you call put , you replace whatever string used to be associated with that key.

It isn't clear what you want the outcome to be, so I can't say how to fix it.

Answer 3

Your code will overwrite the value in each iteration and will give the last value as final one. Instead use a list, add all the values there, and assign that list as map value.

Map<String, List<String>> map = new HashMap<String, List<String>>();
            BufferedReader in = new BufferedReader(new FileReader("wine.data.txt"));
            String line = "";
            while ((line = in.readLine()) != null) {
                String parts[] = line.split(",");
                ArrayList<String> arrList = new ArrayList<String>();
                for(int i = 1; i < parts.length; i++)
                    arrList.add(parts[i]);
                map.put(parts[0], arrList);
                System.out.println(map.toString());
            }
            in.close();

Try this. It should work fine.

Answer 4

Issue is that you were using same key to store each record in row. Its necessary to do a little fundamental change by using List instead of String as value in map. By the end you will get all items in each row as itemList with its own key(1st record). Here is the implementation based on your code:

Map<String, ArrayList<String>> map = new HashMap<>();
BufferedReader in = new BufferedReader(new FileReader("wine.data.txt"));
String line = "";
while ((line = in.readLine()) != null) {
      String parts[] = line.split(",");
      ArrayList<String> valueList = new ArrayList<>(Arrays.asList(parts));
      valueList.remove(0);// get rid of 1st element because it will be used as akey
      map.put(parts[0], valueList);
      System.out.println(map.toString());
}
in.close();