How to add elements of a string array to a string array list?

Question

I am trying to pass a string array as an argument to the constructor of Wetland class; I don't understand how to add the elements of string array to the string array list.

import java.util.ArrayList;  public class Wetland {     private String name;     private ArrayList<String> species;     public Wetland(String name, String[] speciesArr) {         this.name = name;         for (int i = 0; i < speciesArr.length; i++) {             species.add(speciesArr[i]);         }     } } 

Answer 1

You already have built-in method for that: -

List<String> species = Arrays.asList(speciesArr); 

NOTE: - You should use List<String> species not ArrayList<String> species.

Arrays.asList returns a different ArrayList -> java.util.Arrays.ArrayList which cannot be typecasted to java.util.ArrayList.

Then you would have to use addAll method, which is not so good. So just use List<String>

NOTE: - The list returned by Arrays.asList is a fixed size list. If you want to add something to the list, you would need to create another list, and use addAll to add elements to it. So, then you would better go with the 2nd way as below: -

    String[] arr = new String[1];     arr[0] = "rohit";     List<String> newList = Arrays.asList(arr);      // Will throw `UnsupportedOperationException     // newList.add("jain"); // Can't do this.      ArrayList<String> updatableList = new ArrayList<String>();      updatableList.addAll(newList);       updatableList.add("jain"); // OK this is fine.       System.out.println(newList);       // Prints [rohit]     System.out.println(updatableList); //Prints [rohit, jain] 

Answer 2

I prefer this,

List<String> temp = Arrays.asList(speciesArr); species.addAll(temp); 

The reason is Arrays.asList() method will create a fixed sized List. So if you directly store it into species then you will not be able to add any more element, still its not read-only. You can surely edit your items. So take it into temporary list.

Alternative for this is,

Collections.addAll(species, speciesArr); 

In this case, you can add, edit, remove your items.