Duplicated keys in HashMap

Question

I have a strange situation with my HashMaps. While iterating through the keySet() of the HashMap I've got duplicated values. And while trying to get a value I've got NULL.

Here is my HashMap implementation:

    import java.util.ArrayList;
    import java.util.HashMap;

    public class StreetsMap extends HashMap<String, ArrayList<String[]>> {
        public void put(String key, String[] data) {
            ArrayList<String[]> current = get(key);
            if (current == null) {
                current = new ArrayList<String[]>();
                super.put(key, current);
            }
            current.add(data);
        }
    }

While reading lines from a CSV file I'm filling a HashMap with values.
I have something like this in CSV (original list is much longer):

Location_Code, Street_Name, Start, End, OddEven

01001, JustAStreet ST, 1, 11, odd
01001, JustAStreet ST, 17, 47, odd
... more of this
01001, JustAStreet ST, 2, 30, even
01001, JustAStreet ST, 40, 80, even
01001, AnotherStreet ST, 3, 27, odd
01001, AnotherStreet ST, 9, 51, odd
... and even more
01001, AnotherStreet ST, 0, 50, even
01001, AnotherStreet ST, 2, 14, even
01001, AnotherStreet ST, 0, 100, even

I'm splitting a line by comma, trimming values and filling HashMap with data:

    String[] lines = inputText.split("\n");
    
    StreetsMap streetsData = new StreetsMap(); // 

    for (String line : lines) {
        String[] newLine = line.split(",");

        String[] streetData = new String[4];

        streetData[0] = newLine[0].trim();  // Location code
        streetData[1] = newLine[2].trim();  // Start
        streetData[2] = newLine[3].trim();  // End
        streetData[3] = newLine[4].trim();  // OddEven

        streetsData.put(newLine[1].trim(), streetData);

And the problem starts right here. If I iterate through keySet():

    for (String name : streetsData.keySet()) {
        System.out.println(name);
    }

I've got something like:

• JustAStreet
• AnotherStreet
• AnotherStreet
• JustAStreet
• JustAStreet

When I try to access data with .get(key) method during iteration through HashMap sometimes I get null. So I'm loosing values. :(

My question is: how can it be real having a duplicated key in a HashMap? What I'm doing wrong.

UPD: Keys are unique. Found the problem in another class.

Answer 1

how can it be real having a duplicated key in a HashMap? What I'm doing wrong.

Most likely the Strings are not exactly the same. For example AStreet and AStreet{space} look the same but they are not. To make matters worse there are some characters which have no width ;)

I suggest you print Array.toString(text.getBytes()) for each key to see what bytes they have in them.

---

you can get duplicate keys (which you can't get) if you modify a key after it has been added to a map. if the hashcode of a key changes after it is added it can be in the wrong location. this will appear when you iterate but not be seen as a value to replace on a put and you won't find it on a get.

in short you should take care not to change any field use in hashcode, equals or compareTo.