CODEWITHSUNDEEP
javaarraylistreference
Jatinder Singh
Jatinder Singh

Reputation: 9

Array of references to ArrayList Object

I want to know the shortcut for doing this :

class{ ArrayList a1=new ArrayList();
       ArrayList a2=new ArrayList();
       ArrayList a3=new ArrayList();
       .....& so on 
     }

So instead of writing each reference, how can I write an array of references 'with ArrayList' ?

Upvotes: 0

Views: 91

Answers (3)

ChiranjeeviIT
ChiranjeeviIT

Reputation: 529

But creating different references array is not a good design. For example you can create array list array like below:

ArrayList[] a = new ArrayList[4];

Before implementing this you clear with your requirement , why you need to create these many references.

And also while creating ArrayList it's better to use reference creation like below:

List<String> a = new ArrayList<String>();

Always use generics while working on JAVA collections.

For your requirement to store word and it's permutations, I would suggest below process:

Step1: Create WordPermutations class

public Class WordPermutations{
     public string word;
     public ArrayList<String> permutations = new ArrayList<String>();

     public void setWord(String word){
       this.word = word;
      }
     public void setPermutations(ArrayList<string> permutations){
      this.permutations = permutations;
     }
     public String getWord(){
     return this.word;
     }
     public ArrayList<String> getPermuatations(){
     return this.permuations;
     }

}

Step2: Use this class to create your arrayList objects like below:

Class MainPermutation{
public static void main(String args[]){
    // your code to get all your words and their permutations
    // Now add them like below
    ArrayList<WordPermutations> words = new ArrayList<WordPermutations>();
    //your loop to iterate words and their permutations
    for (int i=0;i<words.length;i++){
     WordPermutations wordP = new WordPermutations();
     wordP.setWord(word); //String word
     wordP.setPermutations(permutations); //arraylist of permutations
     words.add(wordP); //adding your word and it's permutations to class
     }
}
}

Step3: Now read your arrayList array accordingly

with above process you can store n number of words.

Hope it helps you.

Upvotes: 0

Srinu Chinka
Srinu Chinka

Reputation: 1491

you can use `List<ArrayList> list = new ArrayList<ArrayList>();`. In this you can add any number of `ArrayList` Objects to `list` reference.

Find the below :

List<ArrayList> list = new ArrayList<ArrayList>();

list.add(new ArrayList());
list.add(new ArrayList());
list.add(new ArrayList());
list.add(new ArrayList());

// ....

list hold ArrayList references in inserted order. You can access the ArrayList using index which zero based.

// to access the ArrayList reference.
ArrayList a1 = list.get(0);

Upvotes: 1

hata
hata

Reputation: 12478

Use an array of ArrayList. And loop.

ArrayList a1, a2, ... , a100;
ArrayList[] arrayLists = new ArrayList[100];

for (ArrayList arrayList : arrayLists) {
    arrayList = new ArrayList();
}

Upvotes: 0

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