O Lista é uma das interfaces de coleção amplamente utilizadas para armazenar a coleção ordenada. A interface List mantém a ordem de inserção dos elementos e também pode armazenar valores duplicados.
Nesta seção, entenderemos como podemos converter uma Lista em um array. Em Java, temos principalmente três maneiras de converter uma lista em um array, que são as seguintes:
- Usando o método get() de List
- Usando o método toArray()
- Usando Stream em Java 8
Usando o método get()
É uma das maneiras mais simples de converter uma lista em um array. Desta forma, acessamos todos os elementos da lista um por um e os adicionamos em um array.
bash verifica se a variável de ambiente está definida
A sintaxe do pegar() O método da interface List é o seguinte:
public Ele get(int pos)
O método get() retorna o elemento que está localizado na posição especificada na lista.
Vamos dar um exemplo de conversão de uma lista em um array para entender como podemos usar o pegar() método da lista.
ConvertListToArrayExample1.java
import java.io.*; import java.util.LinkedList; import java.util.List; // create ConvertListToArrayExample1 class to convert a list into an array class ConvertListToArrayExample1 { // main() method start public static void main(String[] args) { // create linked list by declaring an object of List List names = new LinkedList(); // use add() method of the list to add elements in the linked list names.add('Paul'); names.add('Donal'); names.add('James'); names.add('Robert'); names.add('Mery'); // get size of list and store it into len variable int len = names.size(); // declare and initialize array of type string to store list elements String[] namesArray = new String[ len ]; // iterate list using for loop and add all the elements into namesArray one by one to convert names list into an array for (int i = 0; i <len; i++) namesarray[i]="names.get(i);" print all the elements of array system.out.println('after converting list into an array'); for (int j="0;" < namesarray.length; j++) { system.out.println((j+1)+' element is '+namesarray[j]); } pre> <p> <strong>Output:</strong> </p> <img src="//techcodeview.com/img/java-tutorial/59/convert-list-array-java.webp" alt="Convert List to Array in Java"> <h2>Using toArray() Method</h2> <p>It is another way of converting a list into an array. By using the toArray() method, we can easily convert a list into an array. The toArray() method returns an array having all the elements in the list. The returned array contains elements in the same sequence as the list.</p> <p>The syntax of the <strong>toArray()</strong> method of the List interface is as follows:</p> <pre> public T[] toArray(T[] a) </pre> <p>The toArray() method either accepts an array as a parameter or no parameter, and it returns an array containing all the elements in the list.</p> <p>Let's take another example of converting a list into an array to understand how we can use the <strong>toArray()</strong> method of the list.</p> <p> <strong>ConvertListToArrayExample2.java</strong> </p> <pre> import java.io.*; import java.util.LinkedList; import java.util.List; //create ConvertListToArrayExample2 class to convert a list into an array class ConvertListToArrayExample2 { // main() method start public static void main(String[] args) { // create linked list by declaring an object of List List names = new LinkedList(); // use add() method of the list to add elements in the linked list names.add('Paul'); names.add('Donal'); names.add('James'); names.add('Robert'); names.add('Mery'); // use toArray() method to convert a list into an array String[] namesArray = names.toArray(new String[0]); // print all the elements of the array System.out.println('After converting List into an Array'); for (int j = 0; j <namesarray.length; j++) { system.out.println((j+1)+' element of the array is '+namesarray[j]); } < pre> <p> <strong>Output:</strong> </p> <img src="//techcodeview.com/img/java-tutorial/59/convert-list-array-java-2.webp" alt="Convert List to Array in Java"> <h2>Using Stream</h2> <p>There is one more way of converting a List into an array, i.e., by using Stream introduced in Java8.</p> <p>The syntax of the <strong>toArray()</strong> method of the List interface is as follows:</p> <pre> public T[] toArray(T[] a) </pre> <p>The toArray() method either accepts an array as a parameter or no parameter. It returns an array containing all the elements in the list.</p> <p>Let's take another example of converting a list into an array to understand how we can use the <strong>toArray()</strong> method of the list.</p> <p> <strong>ConvertListToArrayExample3.java</strong> </p> <pre> import java.io.*; import java.util.LinkedList; import java.util.List; //create ConvertListToArrayExample3 class to convert a list into an array class ConvertListToArrayExample3 { // main() method start public static void main(String[] args) { // create linked list by declaring an object of List List names = new LinkedList(); // use add() method of the list to add elements in the linked list names.add('Paul'); names.add('Donal'); names.add('James'); names.add('Robert'); names.add('Mery'); // use stream() method to convert a list into an array String[] namesArray = names.stream().toArray(String[] ::new); // print all the elements of the array System.out.println('After converting List into an Array'); for (int j = 0; j <namesarray.length; j++) { system.out.println((j+1)+' element of the array is '+namesarray[j]); } < pre> <p> <strong>Output:</strong> </p> <img src="//techcodeview.com/img/java-tutorial/59/convert-list-array-java-3.webp" alt="Convert List to Array in Java"> <p>In Java, we mostly use get() and toArray() methods for converting a list into an array. The stream() method is not efficient in comparison of get() and toArray() methods.</p> <hr></namesarray.length;></pre></namesarray.length;></pre></len;> O método toArray() aceita um array como parâmetro ou nenhum parâmetro e retorna um array contendo todos os elementos da lista.
Vamos dar outro exemplo de conversão de uma lista em um array para entender como podemos usar o toArray() método da lista.
ConvertListToArrayExample2.java
import java.io.*; import java.util.LinkedList; import java.util.List; //create ConvertListToArrayExample2 class to convert a list into an array class ConvertListToArrayExample2 { // main() method start public static void main(String[] args) { // create linked list by declaring an object of List List names = new LinkedList(); // use add() method of the list to add elements in the linked list names.add('Paul'); names.add('Donal'); names.add('James'); names.add('Robert'); names.add('Mery'); // use toArray() method to convert a list into an array String[] namesArray = names.toArray(new String[0]); // print all the elements of the array System.out.println('After converting List into an Array'); for (int j = 0; j <namesarray.length; j++) { system.out.println((j+1)+\' element of the array is \'+namesarray[j]); } < pre> <p> <strong>Output:</strong> </p> <img src="//techcodeview.com/img/java-tutorial/59/convert-list-array-java-2.webp" alt="Convert List to Array in Java"> <h2>Using Stream</h2> <p>There is one more way of converting a List into an array, i.e., by using Stream introduced in Java8.</p> <p>The syntax of the <strong>toArray()</strong> method of the List interface is as follows:</p> <pre> public T[] toArray(T[] a) </pre> <p>The toArray() method either accepts an array as a parameter or no parameter. It returns an array containing all the elements in the list.</p> <p>Let's take another example of converting a list into an array to understand how we can use the <strong>toArray()</strong> method of the list.</p> <p> <strong>ConvertListToArrayExample3.java</strong> </p> <pre> import java.io.*; import java.util.LinkedList; import java.util.List; //create ConvertListToArrayExample3 class to convert a list into an array class ConvertListToArrayExample3 { // main() method start public static void main(String[] args) { // create linked list by declaring an object of List List names = new LinkedList(); // use add() method of the list to add elements in the linked list names.add('Paul'); names.add('Donal'); names.add('James'); names.add('Robert'); names.add('Mery'); // use stream() method to convert a list into an array String[] namesArray = names.stream().toArray(String[] ::new); // print all the elements of the array System.out.println('After converting List into an Array'); for (int j = 0; j <namesarray.length; j++) { system.out.println((j+1)+\' element of the array is \'+namesarray[j]); } < pre> <p> <strong>Output:</strong> </p> <img src="//techcodeview.com/img/java-tutorial/59/convert-list-array-java-3.webp" alt="Convert List to Array in Java"> <p>In Java, we mostly use get() and toArray() methods for converting a list into an array. The stream() method is not efficient in comparison of get() and toArray() methods.</p> <hr></namesarray.length;></pre></namesarray.length;> O método toArray() aceita um array como parâmetro ou nenhum parâmetro. Ele retorna um array contendo todos os elementos da lista.
Vamos dar outro exemplo de conversão de uma lista em um array para entender como podemos usar o toArray() método da lista.
ConvertListToArrayExample3.java
import java.io.*; import java.util.LinkedList; import java.util.List; //create ConvertListToArrayExample3 class to convert a list into an array class ConvertListToArrayExample3 { // main() method start public static void main(String[] args) { // create linked list by declaring an object of List List names = new LinkedList(); // use add() method of the list to add elements in the linked list names.add('Paul'); names.add('Donal'); names.add('James'); names.add('Robert'); names.add('Mery'); // use stream() method to convert a list into an array String[] namesArray = names.stream().toArray(String[] ::new); // print all the elements of the array System.out.println('After converting List into an Array'); for (int j = 0; j <namesarray.length; j++) { system.out.println((j+1)+\' element of the array is \'+namesarray[j]); } < pre> <p> <strong>Output:</strong> </p> <img src="//techcodeview.com/img/java-tutorial/59/convert-list-array-java-3.webp" alt="Convert List to Array in Java"> <p>In Java, we mostly use get() and toArray() methods for converting a list into an array. The stream() method is not efficient in comparison of get() and toArray() methods.</p> <hr></namesarray.length;>