如何在java中使用hashmap查找ArrayList中的重复项？

Question

my program is reading large txt files(in MBs) which contain the source ip and destination ip(for example 192.168.125.10,112.25.2.1) ,,,Here read is an ArrayList in which the data is present. i have generated unique ids(uid int type) using srcip and destip and now i am storing in

static ArrayList<Integer[]> prev = new ArrayList<Integer[]>();

where Array is :-

static Integer[] multi1;
multi1 = new Integer[]{(int)uid,count,flag};

i have to print the all uids with there count or their frequencies using hashmap.

Plz give some solution...

for (ArrayList<String> read : readFiles.values())
    {
        if(file_count<=2)
        {
            for(int i=0 ; i<read.size() ; i++)
            {
                String str1=read.get(i).split(",")[0];//get only srcIP
                String str2=read.get(i).split(",")[1];//get only destIP
                StringTokenizer tokenizer1=new StringTokenizer(str1,".");
                StringTokenizer tokenizer2=new StringTokenizer(str2,".");
                if(tokenizer1.hasMoreTokens()&&tokenizer2.hasMoreTokens())
                {
                    sip_oct1=Integer.parseInt(tokenizer1.nextToken());
                    sip_oct2=Integer.parseInt(tokenizer1.nextToken());
                    sip_oct3=Integer.parseInt(tokenizer1.nextToken());
                    sip_oct4=Integer.parseInt(tokenizer1.nextToken());
                    dip_oct1=Integer.parseInt(tokenizer2.nextToken());
                    dip_oct2=Integer.parseInt(tokenizer2.nextToken());
                    dip_oct3=Integer.parseInt(tokenizer2.nextToken());
                    dip_oct4=Integer.parseInt(tokenizer2.nextToken());
                    uid=uniqueIdGenerator(sip_oct1,sip_oct2,sip_oct3,sip_oct4,dip_oct1,dip_oct2,dip_oct3,dip_oct4);
                }
                multi1 = new Integer[]{(int)uid,count,flag};
                prev.add(multi1);
                System.out.println(prev.get(i)[0]);//getting uids from prev
                Map<ArrayList<Integer []> , Integer> map = new HashMap<ArrayList<Integer[]>, Integer>();
                for (int j=0 ; j<prev.size() ; j++) 
                {

                    Integer temp=map.get(prev.get(i)[0]);
                    count = map.get(temp);
                    map.put(temp, (count == null) ? 1 : count++);
                }
                printMap(map);
                System.out.println("uids--->"+prev.get(i)[0]+"    Count---   >"+count+"     flag--->"+prev.get(i)[2]);

            }
        }
        file_count++;
    }
} 
     public static void printMap(Map<ArrayList<Integer[]>, Integer> map)
     {

    for (Entry<ArrayList<Integer[]>, Integer> entry : map.entrySet())
    {
        System.out.println(" Value : "+ entry.getValue()+"key : "+entry.getKey());
    }

}


  public static double uniqueIdGenerator(int oc1,int oc2,int oc3,int oc4,int oc5,int oc6,int oc7,int oc8)
{
    int a,b;
    double c;
    a=((oc1*10+oc2)*10+oc3)*10+oc4;
    b=((oc5*10+oc6)*10+oc7)*10+oc8;
    c=  Math.log(a)+Math.log(b);
    return Math.round(c*1000);
}

Answer 1

Now understanding what you want, there are (at least) 2 ways of doing this.

1st: Make a list with the uid's. Then a second list where you can have a value (your uid) and keep a count. Was thinking of HashMap, but there you can not easily change the count. Maybe an ArrayList of a list with 2 values. Then loop over your list with the uid's, check with a second for loop if the uid is already in the second list. If it is, add one to the count. If it is not, add it to the list.

2nd: Do the same thing, but then with classes (very Java). Then you can put even more info into the class ;)

Hope this helps!

*edit: @RC. indeed gives cleaner code.