显示整个哈希图时遇到问题 - java 堆空间不足

Question

public static void main(String args[]) throws FileNotFoundException, IOException
{


    FileReader in = new FileReader("/home/aoblah/Downloads/file1.txt");
    BufferedReader br = new BufferedReader(in);



   // Scanner in = null;
    String answer = null;
    String verb = null;
    String line = null;
    String [] split_npn = null;
    String [] split_pn = null;
    String [] split_dp2 = null;
    String [] split_dp3 = null;

    HashMap<String, HashMap<String, ArrayList<String>>> hmap = new HashMap<String, HashMap<String, ArrayList<String>>>();

    try {


        while ((line = br.readLine()) != null)
        {
            if(line.contains("verb"))
            {

                 verb = line.substring(0, line.indexOf("("));

                if(line.contains("npn")){
                    String test = line.substring(line.indexOf("npn"));
                    answer = test.substring(test.indexOf("npn"),test.indexof(']')); 

                    answer = answer.replace(",", " " );                        
                    split_npn = answer.split(" ");
                }




                if(line.contains("pn")){
                    String test = line.substring(line.indexOf("pn"));
                    answer = test.substring(test.indexOf("pn"), test.indexOf(']'));
                    answer = answer.replace(",", " " );                        
                    split_pn = answer.split(" ");
                }

                if(line.contains("dp2")){
                    String test = line.substring(line.indexOf("dp2"));
                    answer = test.substring(test.indexOf("dp2"), test.indexOf(']'));
                    answer = answer.replace(",", " " );                        
                    split_dp2 = answer.split(" ");
                }
                if(line.contains("dp3")){
                    String test = line.substring(line.indexOf("dp3"));
                    answer = test.substring(test.indexOf("dp3"), test.indexOf(']'));
                    answer = answer.replace(",", " " ); 
                    split_dp3 = answer.split(" ");
                }                    


            }

            if(split_npn != null){
                ArrayList<String> npn = new ArrayList<String>();
                hmap.put(verb, new HashMap<String, ArrayList<String>>());
                for(int i = 1; i< split_npn.length; i++){
                    npn.add(split_npn[i]);
                }
                npn.trimToSize();
                hmap.get(verb).put("npn", npn);
            }

            if(split_pn != null){
                ArrayList<String> pn = new ArrayList<String>();
                hmap.put(verb, new HashMap<String, ArrayList<String>>());
                for(int i = 1; i< split_pn.length; i++){
                    pn.add(split_pn[i]);
                }
                pn.trimToSize();
                hmap.get(verb).put("pn", pn);
            }                

            if(split_dp2 != null){
                ArrayList<String> dp2 = new ArrayList<String>();
                hmap.put(verb, new HashMap<String, ArrayList<String>>());
                for(int i = 1; i< split_dp2.length; i++){
                    dp2.add(split_dp2[i]);
                }
                dp2.trimToSize();
                hmap.get(verb).put("dp2", dp2);
            }                                

            if(split_dp3 != null){
                ArrayList<String> dp3 = new ArrayList<String>();
                hmap.put(verb, new HashMap<String, ArrayList<String>>());
                for(int i = 1; i< split_dp3.length; i++){
                    dp3.add(split_dp3[i]);
                }
                dp3.trimToSize();
                hmap.get(verb).put("dp3", dp3);
            } 

            System.out.println(hmap);

        }

    }


    catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

The file contains entries such as

calm(verb,naux,[nullobj,[dp2,down],[dp3,down]],calm).
calms(verb,[sg],calm).
calmed(verb,[sg,pl,en],calm).
calm(verb,[pl,inf],calm).
calming(verb,[ing],calm).
calmly(adv,mv,calmly).
calmness(noun,[sg],calmness).

I am storing all the verbs, categories of the prepositions associated with it and the prepositions in a nested hash map. I have no trouble when printing only a particular category of prepositions associated with the verb, but when I display the whole hashmap the programs just runs and never stops...ending up in java out of space heap error. How can i fix this memory problem?

Answer 1

One suggestion is that instead of doing System.out.println(hmap);

Try to print it out sequentually:

for(String outerKey: hmap.keySet())
{
   System.out.println(outerKey + ": ");
   Map inner = hmap.get(outerKey);
   for(String innerKey : innerMap)
   {
    System.out.print(innerKey + ": ");
    System.out.println(innterMap.get(innerKey).toString());
   }

}

Answer 2

You print the map using

System.out.println(hmap)

This uses the toString() method of the HashMap which build one large string in memory for the whole output. Depending on the size of you input file read this can be much memory.

It would be better to print the map iterating the entries:

for (Object e : hmap.entrySet()) {
  System.out.print(e);
}
System.out.println();

This will allocate memory for one entry, print it, hand it to the garbage collector and take the next.