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
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~ Asked on 2012-03-05 19:37:28
Foo array = list.toArray(new Foo);
Foo array = new Foo[list.size()]; list.toArray(array); // fill the array
Note that this works only for arrays of reference types. For arrays of primitive types, use the traditional way:
List<Integer> list = ...; int array = new int[list.size()]; for(int i = 0; i < list.size(); i++) array[i] = list.get(i);
It is recommended now to use
list.toArray(new Foo);, not
From JetBrains Intellij Idea inspection:
There are two styles to convert a collection to an array: either using a pre-sized array (like c.toArray(new String[c.size()])) or using an empty array (like c.toArray(new String).
In older Java versions using pre-sized array was recommended, as the reflection call which is necessary to create an array of proper size was quite slow. However since late updates of OpenJDK 6 this call was intrinsified, making the performance of the empty array version the same and sometimes even better, compared to the pre-sized version. Also passing pre-sized array is dangerous for a concurrent or synchronized collection as a data race is possible between the size and toArray call which may result in extra nulls at the end of the array, if the collection was concurrently shrunk during the operation.
This inspection allows to follow the uniform style: either using an empty array (which is recommended in modern Java) or using a pre-sized array (which might be faster in older Java versions or non-HotSpot based JVMs).
~ Answered on 2012-03-05 19:39:39
An alternative in Java 8:
String strings = list.stream().toArray(String::new);
Since Java 11:
String strings = list.toArray(String::new);
~ Answered on 2014-04-20 16:30:28