into - list to array java 8




Convert list to array in Java (8)

An alternative in Java 8:

String[] strings = list.stream().toArray(String[]::new);

How can I convert a List to an Array in Java?

Check the code below:

ArrayList<Tienda> tiendas;
List<Tienda> tiendasList; 
tiendas = new ArrayList<Tienda>();

Resources res = this.getBaseContext().getResources();
XMLParser saxparser =  new XMLParser(marca,res);

tiendasList = saxparser.parse(marca,res);
tiendas = tiendasList.toArray();

this.adaptador = new adaptadorMarca(this, R.layout.filamarca, tiendas);
setListAdapter(this.adaptador);  

I need to populate the array tiendas with the values of tiendasList.


Best thing I came up without Java 8 was:

public static <T> T[] toArray(List<T> list, Class<T> objectClass) {
    if (list == null) {
        return null;
    }

    T[] listAsArray = (T[]) Array.newInstance(objectClass, list.size());
    list.toArray(listAsArray);
    return listAsArray;
}

If anyone has a better way to do this, please share :)


Example taken from this page: http://www.java-examples.com/copy-all-elements-java-arraylist-object-array-example

import java.util.ArrayList;

public class CopyElementsOfArrayListToArrayExample {

  public static void main(String[] args) {
    //create an ArrayList object
    ArrayList arrayList = new ArrayList();

    //Add elements to ArrayList
    arrayList.add("1");
    arrayList.add("2");
    arrayList.add("3");
    arrayList.add("4");
    arrayList.add("5");

    /*
      To copy all elements of java ArrayList object into array use
      Object[] toArray() method.
    */

    Object[] objArray = arrayList.toArray();

    //display contents of Object array
    System.out.println("ArrayList elements are copied into an Array.
                                                  Now Array Contains..");
    for(int index=0; index < objArray.length ; index++)
      System.out.println(objArray[index]);
  }
}

/*
Output would be
ArrayList elements are copied into an Array. Now Array Contains..
1
2
3
4
5

For ArrayList the following works:

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

//... add values

Foo[] resultArray = new Foo[list.size()];
resultArray = list.toArray(resultArray);

I think this is the simplest way:

Foo[] array = list.toArray(new Foo[0]);

This (Ondrej's answer):

Foo[] array = list.toArray(new Foo[0]);

Is the most common idiom I see. Those who are suggesting that you use the actual list size instead of "0" are misunderstanding what's happening here. The toArray call does not care about the size or contents of the given array - it only needs its type. It would have been better if it took an actual Type in which case "Foo.class" would have been a lot clearer. Yes, this idiom generates a dummy object, but including the list size just means that you generate a larger dummy object. Again, the object is not used in any way; it's only the type that's needed.


Try this:

List list = new ArrayList();
list.add("Apple");
list.add("Banana");

Object[] ol = list.toArray();

You can use toArray() api as follows,

ArrayList<String> stringList = new ArrayList<String>();
stringList.add("ListItem1");
stringList.add("ListItem2");
String[] stringArray = new String[stringList.size()];
stringArray = stringList.toArray(stringList);

Values from the array are,

for(String value : stringList)
{
    System.out.println(value);
}






arraylist