Java Program to Convert an Array into a List - GeeksforGeeks

09 Feb, 2022
Given an array. Your task is to convert the given array into a list in Java.
Examples: 
Input: Array: [Geeks, forGeeks, A computer Portal] 
Output: List: [Geeks, forGeeks, A computer Portal]

Input: Array: [1, 2, 3, 4, 5] 
Output: List: [1, 2, 3, 4, 5] 
Arrays: An array is a group of like-typed variables that are referred to by a common name. An array can contain primitives data types as well as objects of a class depending on the definition of the array. In the case of primitives data types, the actual values are stored in contiguous memory locations. In the case of objects of a class, the actual objects are stored in a heap segment.
List: The Java.util.List is a child interface of Collection. It is an ordered collection of objects in which duplicate values can be stored. Since List preserves the insertion order, it allows positional access and insertion of elements. List Interface is implemented by ArrayList, LinkedList, Vector, and Stack classes.
There are numerous approaches to do the conversion of an array to a list in Java. A few of them are listed below.
Brute Force or Naive Method
Using Arrays.asList() Method
Using Collections.addAll() Method
Using Java 8 Stream API
Using Guava Lists.newArrayList()
In this method, an empty List is created and all elements present in the Array are added to it one by one.
Algorithm:
Get the Array to be converted.Create an empty ListIterate through the items in the Array.For each item, add it to the ListReturn the formed List
Get the Array to be converted.
Create an empty List
Iterate through the items in the Array.
For each item, add it to the List
Return the formed List
Java
// Java Program to convert// Array to List  import java.util.*;import java.util.stream.*;  class GFG {      // Generic function to convert an Array to List    public static <T> List<T> convertArrayToList(T array[])    {          // Create an empty List        List<T> list = new ArrayList<>();          // Iterate through the array        for (T t : array) {            // Add each element into the list            list.add(t);        }          // Return the converted List        return list;    }      public static void main(String args[])    {        // Create an Array        String array[]            = { "Geeks", "forGeeks", "A Computer Portal" };          // Print the Array        System.out.println("Array: "                           + Arrays.toString(array));          // convert the Array to List        List<String> list = convertArrayToList(array);          // Print the List        System.out.println("List: " + list);    }}
Array: [Geeks, forGeeks, A Computer Portal]
List: [Geeks, forGeeks, A Computer Portal]
In this method, the Array is passed as the parameter into the List constructor with the help of the Arrays.asList() method.
Algorithm: 
Get the Array to be converted.Create the List bypassing the Array as a parameter in the constructor of the List with the help of Arrays.asList() methodReturn the formed List
Get the Array to be converted.
Create the List bypassing the Array as a parameter in the constructor of the List with the help of Arrays.asList() method
Return the formed List
Java
// Java Program to convert// Array to List  import java.util.*;import java.util.stream.*;  class GFG {      // Generic function to convert an Array to List    public static <T> List<T> convertArrayToList(T array[])    {          // Create the List by passing the Array        // as parameter in the constructor        List<T> list = Arrays.asList(array);          // Return the converted List        return list;    }      public static void main(String args[])    {        // Create an Array        String array[]            = { "Geeks", "forGeeks", "A computer Portal" };          // Print the Array        System.out.println("Array: "                           + Arrays.toString(array));          // convert the Array to List        List<String> list = convertArrayToList(array);          // Print the List        System.out.println("List: " + list);    }}
Array: [Geeks, forGeeks, A computer Portal]
List: [Geeks, forGeeks, A computer Portal]
Since List is a part of the Collection package in Java. Therefore the Array can be converted into the List with the help of the Collections.addAll() method.
Algorithm: 
Get the Array to be converted.Create an empty List.Add the array into the List by passing it as the parameter to the Collections.addAll() method.Return the formed List
Get the Array to be converted.
Create an empty List.
Add the array into the List by passing it as the parameter to the Collections.addAll() method.
Return the formed List
Java
// Java Program to convert// Array to List  import java.util.*;import java.util.stream.*;  class GFG {      // Generic function to convert an Array to List    public static <T> List<T> convertArrayToList(T array[])    {          // Create the List by passing the Array        // as parameter in the constructor        List<T> list = new ArrayList<>();          // Add the array to list        Collections.addAll(list, array);          // Return the converted List        return list;    }      public static void main(String args[])    {        // Create an Array        String array[]            = { "Geeks", "forGeeks", "A computer Portal" };          // Print the Array        System.out.println("Array: "                           + Arrays.toString(array));          // convert the Array to List        List<String> list = convertArrayToList(array);          // Print the List        System.out.println("List: " + list);    }}
Array: [Geeks, forGeeks, A computer Portal]
List: [Geeks, forGeeks, A computer Portal]
An ArrayList constructor can take another collection object to construct a new list containing the elements of the specified array.
Algorithm: 
Get the Array to be converted.Convert the array to StreamConvert the Stream to List using Collectors.toList()Collect the formed list using the collect() methodReturn the formed List
Get the Array to be converted.
Convert the array to Stream
Convert the Stream to List using Collectors.toList()
Collect the formed list using the collect() method
Return the formed List
Java
// Java Program to convert// Array to List in Java 8  import java.util.*;import java.util.stream.*;  class GFG {      // Generic function to convert array to list    public static <T> List<T> convertArrayToList(T array[])    {        // create a list from the Array        return Arrays.stream(array).collect(            Collectors.toList());    }      public static void main(String args[])    {        // Create an Array        String array[]            = { "Geeks", "forGeeks", "A computer Portal" };          // Print the Array        System.out.println("Array: "                           + Arrays.toString(array));          // convert the Array to List        List<String> list = convertArrayToList(array);          // Print the List        System.out.println("List: " + list);    }}
Array: [Geeks, forGeeks, A computer Portal]
List: [Geeks, forGeeks, A computer Portal]
Lists.newArrayList() creates a mutable ArrayList instance containing the elements of the specified array. 
Algorithm: 
Get the Array to be converted.Create an empty List.Add the array into the List by passing it as the parameter to the Lists.newArrayList() method.Return the formed List
Get the Array to be converted.
Create an empty List.
Add the array into the List by passing it as the parameter to the Lists.newArrayList() method.
Return the formed List
Java
// Java Program to convert// Array to List in Java 8  import static com.google.common.collect.Lists.*;  import java.util.*;import java.util.stream.*;  class GFG {      // Generic function to convert array to list    public static <T> List<T> convertArrayToList(T array[])    {        // create a list from the Array        return Lists.newArrayList(array);    }      public static void main(String args[])    {        // Create an Array        String array[]            = { "Geeks", "forGeeks", "A computer Portal" };          // Print the Array        System.out.println("Array: "                           + Arrays.toString(array));          // convert the Array to List        List<String> list = convertArrayToList(array);          // Print the List        System.out.println("List: " + list);    }}
Output
Array: [Geeks, forGeeks, A computer Portal]
List: [Geeks, forGeeks, A computer Portal]
nishkarshgandhi
Java-Array-Programs
Java-Arrays
java-list
Java-List-Programs
Java
Java Programs
Java
Writing code in comment?
Please use ide.geeksforgeeks.org,
generate link and share the link here.
Object Oriented Programming (OOPs) Concept in Java
HashMap in Java with Examples
Stream In Java
Interfaces in Java
How to iterate any Map in Java
Convert a String to Character Array in Java
Java Programming Examples
Convert Double to Integer in Java
Implementing a Linked List in Java using Class
How to Iterate HashMap in Java?