CODEWITHSUNDEEP
javaloopsarraylistdata-structures
Betafish
Betafish

Reputation: 1262

Lookup in arrayList

I am trying to do a lookup for a corresponding value for an entry item in an arraylist (alphanumeric value and its hashcode).

The use of hashmap was dropped to allow duplication of objects(keys).

ArrayList<Object[]> pNArrayList = new ArrayList<Object[]>(); contains

[101E2571G103, -1162488899]
[101E2571G103, -1162488899]
[116E3139P001, -1561106156]
[314B7159G003, -1344220682]
[117E3640G025, -1595019143]
[117E3640G025, -1595019143]

For an input, inputID of type long

for(int i=0; i< pNHashArrayList.size();i++) {
            if(pNArrayList.get(i)[1].equals(inputID)){
                System.out.println(pNArrayList.get(i)[0]);
            }
            else {
                System.out.println(pNArrayList.get(i)[0] + " and "+ pNArrayList.get(i)[1] +" No Match Found");
            }
        }

The else and SysOutstatement thereafter were included only to cross validate.

output:

 101E2571G103 and -1162488899 No Match Found
 101E2571G103 and -1162488899 No Match Found
 116E3139P001 and -1561106156 No Match Found
 314B7159G003 and -1344220682 No Match Found
 117E3640G025 and -1595019143 No Match Found
 117E3640G025 and -1595019143 No Match Found

I think, the problem might be in the pNArrayList.get(i)[1].equals(inputID)?. Need some suggestions on this.

Also, my actual dataset will have around 10,000 entires, would the lookup by looping have problem with runtime computations?

Upvotes: 0

Views: 1143

Answers (2)

Mahendra
Mahendra

Reputation: 1426

Good approach is suggested by @sharonbn, but you can try this to run your existing code :

        if( ((Long)pNArrayList.get(i)[1]) == inputID){
            System.out.println(pNArrayList.get(i)[0]);
        }
        else {
            System.out.println(pNArrayList.get(i)[0] + " and "+ pNArrayList.get(i)[1] +" No Match Found");
        }
    }

Upvotes: 0

Sharon Ben Asher
Sharon Ben Asher

Reputation: 14328

I don't know how you build your data structure. However, a better design is to have a Map<Long, List<Object>> with the Long inputID as key, and the value can be a List of Objects that all belong to the same ID. This way you support multiple values for the same key and the lookup is O(1)

regarding the equals, it is Object's equals that is invoked, rather than Long one. The proposed data structure should solve this problem as well.

Upvotes: 2

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