[java] How to add elements of a string array to a string array list?

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]);
        }
    }
}

public class duplicateArrayList {


    ArrayList al = new ArrayList();
    public duplicateArrayList(Object[] obj) {

        for (int i = 0; i < obj.length; i++) {

            al.add(obj[i]);
        }

        Iterator iter = al.iterator();
        while(iter.hasNext()){

            System.out.print(" "+iter.next());
        }
    }

    public static void main(String[] args) {


    String[] str = {"A","B","C","D"};

    duplicateArrayList dd = new duplicateArrayList(str);

    }

}

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.

ArrayList<String> arraylist= new ArrayList<String>();

arraylist.addAll( Arrays.asList("mp3 radio", "presvlake", "dizalica", "sijelice", "brisaci farova", "neonke", "ratkape", "kuka", "trokut")); 

Thought I'll add this one to the mix:

Collections.addAll(result, preprocessor.preprocess(lines));

This is the change that Intelli recommends.

from the javadocs:

Adds all of the specified elements to the specified collection._x000D_
Elements to be added may be specified individually or as an array._x000D_
The behavior of this convenience method is identical to that of_x000D_
<tt>c.addAll(Arrays.asList(elements))</tt>, but this method is likely_x000D_
to run significantly faster under most implementations._x000D_
 _x000D_
When elements are specified individually, this method provides a_x000D_
convenient way to add a few elements to an existing collection:_x000D_
<pre>_x000D_
Collections.addAll(flavors, "Peaches 'n Plutonium", "Rocky Racoon");_x000D_
</pre>

You should instantiate your ArrayList before trying to add items:

private List<String> species = new ArrayList<String>();

Arrays.asList is the handy function available in Java to convert an array variable to List or Collection. For better under standing consider the below example:

package com.stackoverflow.works;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Wetland {
    private String name;
    private List<String> species = new ArrayList<String>();

    public Wetland(String name, String[] speciesArr) {
        this.name = name;
        this.species = Arrays.asList(speciesArr);
    }

    public void display() {
        System.out.println("Name: " + name);
        System.out.println("Elements in the List");
        System.out.println("********************");
        for (String string : species) {
            System.out.println(string);
        }
    }

    /*
     * @Description: Method to test your code
     */
    public static void main(String[] args) {
        String name = "Colors";
        String speciesArr[] = new String [] {"red", "blue", "green"};
        Wetland wetland = new Wetland(name, speciesArr);
        wetland.display();
    }

}

Output:

Arrays.asList() method simply returns List type

char [] arr = { 'c','a','t'};    
ArrayList<Character> chars = new ArrayList<Character>();

To add the array into the list, first convert it to list and then call addAll

List arrList = Arrays.asList(arr);
chars.addAll(arrList);

The following line will cause compiler error

chars.addAll(Arrays.asList(arr));

Arrays.asList is bridge between Array and collection framework and it returns a fixed size List backed by Array.

species = Arrays.asList(speciesArr);

In Java 8, the syntax for this simplifies greatly and can be used to accomplish this transformation succinctly.

Do note, you will need to change your field from a concrete implementation to the List interface for this to work smoothly.

public class Wetland {
    private String name;
    private List<String> species;
    public Wetland(String name, String[] speciesArr) {
        this.name = name;
        species = Arrays.stream(speciesArr)
                        .collect(Collectors.toList());
    }
}

Use asList() method. From java Doc asList

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