HashMap containsKey always returns false for same string

Question

I am parsing from a file where I have city names and distances to other cities in this format:

"San Antonio" 
"San Francisco" 
Washington 

"San Francisco"--Weed [305]
"San Francisco"--"Wisconsin Dells" [2189]
Washington--"San Jose" [2909]

I think that the problem is that when I chop up the strings, it creates different objects and for some reason, the String.equals and/or the hashcode() gives different results. Because of this, the Map.get(key) returns null values. I however do not know how to fix this.

public class spanning {
private static HashMap<String, HashMap<String, Integer>> map = new HashMap<String, HashMap<String, Integer>>();
public static void main(String[] args) throws IOException {
    BufferedReader read = new BufferedReader(new FileReader(args[0]));
    String temp;
    while ((temp = read.readLine()) != null) {
        if (temp.contains("[")) {
            String[] parts = temp.split("--");
            String[] parts2 = parts[1].split(" \\[");
            Scanner scan;
            scan = new Scanner(parts2[1]).useDelimiter("\\D");
            int o = scan.nextInt();
            map.get(parts[0]).put(parts2[0], o);
        } else {
            map.put(temp, new HashMap<String, Integer>());

        }
    }
    System.out.println("Finished!");
}

}

`String.equals()` will compare the text in the case of Strings. Have you got an example of what failed exactly? — achAmháin, May 01 '18 at 15:09
Yeah, I added a line boolean test = map.containsKey(parts[0]) above the map.get()and it returned false — Slayahh, May 01 '18 at 15:11
If you print `parts[0]` and the keys from the map, does `parts[0]` exist in it? — achAmháin, May 01 '18 at 15:12
You're putting the whole of `temp` into the hashmap as the key, not `parts[0]`- did you mean to do that? In that `else` - check what `temp` looks like just before you put it in — David Lavender, May 01 '18 at 15:12
If `temp` doesn't contain a distance, it is just put in the map as ""San Antonio"" or "Washington". Going to try what @notyou said now. — Slayahh, May 01 '18 at 15:16
I found the error I think, it appears that all of my input from cities have an extra whitespace after them, so I'm going to try to remove that and try again, thanks. — Slayahh, May 01 '18 at 15:21

score 0 · Answer 1 · answered May 01 '18 at 16:58

I've ran your code and below is the map when it reach a row that prints "Finished":

map = {HashMap@634}  size = 4
 0 = {HashMap$Node@640} "" -> " size = 0"
 1 = {HashMap$Node@641} ""San Antonio"" -> " size = 0"
  key = ""San Antonio""
  value = {HashMap@647}  size = 0
 2 = {HashMap$Node@642} ""San Francisco"" -> " size = 2"
  key = ""San Francisco""
  value = {HashMap@649}  size = 2
   0 = {HashMap$Node@654} "Weed" -> "305"
   1 = {HashMap$Node@655} ""Wisconsin Dells"" -> "2189"
 3 = {HashMap$Node@643} "Washington" -> " size = 1"
  key = "Washington"
  value = {HashMap@651}  size = 1
   0 = {HashMap$Node@662} ""San Jose"" -> "2909"

What was the exact problem? Did you see what was the values of your map right before it goes out of the method?

HashMap containsKey always returns false for same string

1 Answers1