How to initialize ArrayList with Array in Java | Copy from Array to List - One Liner Example

Initializing list while declaring it is very convenient for quick use. If
you have been using Java programming language for quite some time then you must
be familiar with syntax of array in Java and how to initialize an array
in the same line while declaring it as show below:

String[] oldValues = new String[] {"list"
, "set" , "map"};

or even shorter :

String[] values = {"abc","bcd",
"def"};

Similarly we can also create List  and initialize it at same line, popularly
known as initializing List in one line example. Arrays.asList() is used
for that purpose which returns a fixed size List backed by Array. By the way
don’t confuse between Immutable
or read only List which doesn’t allow any modification operation including set(index) which is
permitted in fixed length List.Here is an example of creating and initializing List in one
line :

Java program to create and initialize List
in one line

Here is a Java program which creates and initialize List in one line
using Array. Arrays.asList() method is used to initialize List
in one line and it takes an Array which you can create at the time of calling
this method itself. Arrays.asList() also use Generics
to provide type-safety and this example can be written using Generics as well.

import java.util.Arrays;

import java.util.List;



/**

 * How to create and initialize List in same line, Similar to Array
in Java.

 * Arrays.asList() method is used to initialize a List from Array but List

 * returned by this method is a fixed size List and you can not change its
size.

 * Which means adding and deleting elements from List is not allowed.

 *

 * @author Javin Paul

 */

public class
ListExample {



    public static void
main(String args[]) {

   

      //declaring and
initializing array in one line

      String[]
oldValues = new String[] {"list" , "set"
, "map"};

      String[] values
= {"abc","bcd", "def"};

   

      //initializing list with
array in java

      List init = Arrays.asList(values);

      System.out.println("size: " + init.size() +" list: "
+ init);

   

      //initializing List in one
line in Java

      List oneLiner = Arrays.asList("one" , "two",
"three");

      System.out.println("size: " + init.size() +" list: "
+ oneLiner);

   

      //List returned by
Arrays.asList is fixed size and doesn't support add or remove

      oneLiner.add("four"); //will throw java.lang.UnsupportedOperationException

      //oneLiner.remove("one");
//also throw java.lang.UnsupportedOperationException

    }

}



Output:

size: 3 list: [abc,
bcd, def]

size: 3 list: [one,
two, three]

Exception in thread "main"
java.lang.UnsupportedOperationException

        at java.util.AbstractList.add(AbstractList.java:131)

        at java.util.AbstractList.add(AbstractList.java:91)

        at test.ExceptionTest.main(ExceptionTest.java:32)

As shown in above example its important to remember that List returned by
Arrays.asList() can not be used as regular List for further adding
or removing elements. Its kind of fixed length List which doesn't support
addition and removal of elements. Nevertheless its clean solution for creating and
initializing List in Java in one line, quite useful for testing purpose.

Related Java Collection tutorials from Javarevisited Blog

How
to sort ArrayList in descending and ascending order in Java

How
to remove duplicate object from ArrayList in Java

Difference
between Set and List in Java

How
to loop or iterate ArrayList in Java with example

How
to convert Array to ArrayList in Java

Difference
between LinkedList and ArrayList in Java

Source:http://javarevisited.blogspot.com/2012/12/how-to-initialize-list-with-array-in-java.html