Converting String array to java.util.List

How do I convert a String array to a java.util.List?

8 Answers

List<String> strings = Arrays.asList(new String[]{"one", "two", "three"}); 

This is a list view of the array, the list is partly unmodifiable, you can't add or delete elements. But the time complexity is O(1).

If you want a modifiable a List:

List<String> strings = new ArrayList<String>(Arrays.asList(new String[]{"one", "two", "three"})); 

This will copy all elements from the source array into a new list (complexity: O(n))

Use the static List list = Arrays.asList(stringArray) or you could just iterate over the array and add the strings to the list.

import java.util.Collections; List myList = new ArrayList(); String[] myArray = new String[] {"Java", "Util", "List"}; Collections.addAll(myList, myArray); 

The Simplest approach:

String[] stringArray = {"Hey", "Hi", "Hello"}; List<String> list = Arrays.asList(stringArray); 

First Step you need to create a list instance through Arrays.asList();

String[] args = new String[]{"one","two","three"}; List<String> list = Arrays.asList(args);//it converts to immutable list 

Then you need to pass 'list' instance to new ArrayList();

List<String> newList=new ArrayList<>(list); 

As of Java 8 and Stream API you can use Arrays.stream and Collectors.toList:

String[] array = new String[]{"a", "b", "c"}; List<String> list = Arrays.stream(array).collect(Collectors.toList()); 

This is practical especially if you intend to perform further operations on the list.

String[] array = new String[]{"a", "bb", "ccc"}; List<String> list = Arrays.stream(array) .filter(str -> str.length() > 1) .map(str -> str + "!") .collect(Collectors.toList()); 

On Java 14 you can do this

List<String> strings = Arrays.asList("one", "two", "three"); 

If the result should be a readonly list then you can use List.of(nameOfArray)

@Test public void shouldMapArrayToList(){ // given var testArray = new String[]{"1", "2", "3" }; // when List<String> result = List.of(testArray); // then assertEquals("1", result.get(0)); assertEquals("2", result.get(1)); assertEquals("3", result.get(2)); }