HashMap repeating the last element

Question

I am trying to create a HashMap in a HashMap so it will be easier for me to access elements of it in the future as shown below.

The problem is it only repeating the last elements of the while loop and not the rest of it.

HashMap<String,String> result = new HashMap<>();
HashMap<Integer, HashMap<String,String>> fr = new HashMap<>();

int i = 0;
try {
    ResultSet rq = qexec.execSelect();
    // ResultSetFormatter.out(System.out, rq, query);

    // get result from SPARQL query
    while (rq.hasNext()) {
        QuerySolution soln = rq.next();
        id = soln.getLiteral("?id").getLexicalForm();
        //...
        result.put("id",id);
        //...
        if (soln.getLiteral("?wateruse") != null) {
            wateruse = soln.getLiteral("?wateruse").getLexicalForm();
            //...
            result.put("wateruse",wateruse);
        } else {
            System.out.println("NO");
        }               

        fr.put(i, result);
        i++;
    }
} finally {
    qexec.close();
}

This is how the result should be:

John001
High usage
John002
John003
Smith001
Moderate
Smith002
Smith003
...
Kevin001
Low usage

But fr only repeats Kevin001 and Low usage without the rest.

I've tried to put fr.put(i,result) outside the loop but that still does not give the correct result.

EDIT

I tried to print all elements from fr that shows the repeating elements.

finally {

            qexec.close();
        }


        for (int index : fr.keySet()) {
              for(Map.Entry<String, String> entry :result.entrySet()) {
                System.out.println(index + " = " + entry.getKey() + " : " + entry.getValue());
            }
        }

UPDATE - SOLUTION

Declare HashMap inside the loop as mentioned in comments below.

To print nested HashMap, no need to use result. I did as shown below and it prints both outermap and innermap as well.

        for (int k=0;  k < fr.size(); k++) {
            HashMap<String,String> innermap = fr.get(k);
            for(Map.Entry<String, String> e : innermap.entrySet()) {
                System.out.println(k + " = " + e.getKey() + " : " + e.getValue());
            }
        }

creating map object inside loop will solve you problem. like : result = new HashMap<>(); — Devram Kandhare, Aug 23 '17 at 03:38
In your edit to print all elements, you should not be using "result.entryset" (which has nothing to do with the outer for loop), but "fr.get(index)" — racraman, Aug 23 '17 at 04:01
You're printing the values from the last entry in the map because you're printing the `result` map. That will always have the data from the last iteration through the loop. Instead, get the values from `fr` as you loop through it (updated with details on how to do that). — nbrooks, Aug 23 '17 at 04:01

nbrooks · Accepted Answer · 2017-08-23T04:00:24.920

You're adding the same result map to your parent map each time through the loop. Create a new instance of result each time through the loop:

Map<String, String> result = new HashMap<>();
Map<Integer, Map<String, String>> fr = new HashMap<>();

int i = 0;
try {

    ResultSet rq = qexec.execSelect();

    while (rq.hasNext()) {

        // Create your new HashMap inside the loop:
        result = new HashMap<>();

        QuerySolution soln = rq.next();

        id = soln.getLiteral("?id").getLexicalForm();
        //...

        result.put("id",id);
        //...

        if (soln.getLiteral("?wateruse") != null) {

            wateruse = soln.getLiteral("?wateruse").getLexicalForm();
            //...
            result.put("wateruse",wateruse);
        }
        else {
            System.out.println("NO");
        }               

        fr.put(i,result);
        i++;
    }
}

To print the results from fr an its nested map, you can do something like this:

for (Map<String, String> map : fr.values()) {
    for(Map.Entry<String, String> e : map.entrySet()) {
        System.out.println(index + " = " + e.getKey() 
            + " : " + e.getValue());
    }
}

Can you highlight the part in the code where you have changed something? — Zabuzard, Aug 23 '17 at 03:37
where does `index` comes from in `System.out.println(index + " = " + e.getKey() `? — kaixas K, Aug 23 '17 at 07:02

Umar Hussain · Answer 2 · 2017-08-23T04:01:00.503

2

Try this a small change here, place the "result" map creation in while loop

Map<Integer, Map<String, String>> fr = new HashMap<>();

int i = 0;
try {

    ResultSet rq = qexec.execSelect();

    while (rq.hasNext()) {
        Map<String, String> result = new HashMap<>();

        QuerySolution soln = rq.next();

        id = soln.getLiteral("?id").getLexicalForm();
        //...

        result.put("id",id);
        //...

        if (soln.getLiteral("?wateruse") != null) {

            wateruse = soln.getLiteral("?wateruse").getLexicalForm();
            //...
            result.put("wateruse",wateruse);
        }
        else {
            System.out.println("NO");
        }               

        fr.put(i,result);
        i++;
    }
}

This for loop to print elemenets:

for (int i=0;i< fr.size();i++){
    Map<String,String> element= fr.get(i);
//  use the element here.

}

edited Aug 23 '17 at 04:01

answered Aug 23 '17 at 03:43

Umar Hussain

3,461
1
16
38

But then I cannot access `result` from outside the loop. – kaixas K Aug 23 '17 at 03:45
1

@kaixasK You shouldn't be using `result` outside of the loop anyway. After the loop it will only have the last value. What are you using that for? – nbrooks Aug 23 '17 at 03:47
Then you can declare the object outside loop and in loop create new element `result = new HashMap<>();` But why do you need result object outside loop, you have the "fr" already available to you to access all elements. – Umar Hussain Aug 23 '17 at 03:48
How can I do so since it is `HashMap` in another `HashMap`? – kaixas K Aug 23 '17 at 03:54
@kaixasK see my edited answer please. – Umar Hussain Aug 23 '17 at 04:01

HashMap repeating the last element

2 Answers2