ה רשימה הוא אחד ממשקי האיסוף הנפוצים המשמשים לאחסון האוסף שהוזמן. ממשק הרשימה שומר על סדר ההכנסה של אלמנטים ויכול לאחסן גם ערכים כפולים.
בחלק זה, נבין כיצד נוכל להמיר רשימה למערך. ב-Java, יש לנו בעיקר שלוש דרכים להמיר רשימה למערך שהן כדלקמן:
- שימוש בשיטת get() של List
- שימוש בשיטת toArray()
- שימוש ב-Stream ב-Java 8
שימוש בשיטת get()
זוהי אחת הדרכים הפשוטות ביותר להמיר רשימה למערך. בדרך זו, אנו ניגשים לכל רכיבי הרשימה בזה אחר זה ומוסיפים אותם למערך.
סנטוס נגד rhel
התחביר של ה לקבל() השיטה של ממשק הרשימה היא כדלקמן:
public Ele get(int pos)
השיטה get() מחזירה את האלמנט שנמצא במיקום שצוין ברשימה.
בואו ניקח דוגמה להמרת רשימה למערך כדי להבין כיצד אנו יכולים להשתמש ב- לקבל() שיטת הרשימה.
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;> השיטה toArray() מקבלת מערך כפרמטר או ללא פרמטר, והיא מחזירה מערך המכיל את כל האלמנטים ברשימה.
ניקח דוגמה נוספת להמרת רשימה למערך כדי להבין כיצד אנו יכולים להשתמש ב- toArray() שיטת הרשימה.
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;> השיטה toArray() מקבלת מערך כפרמטר או ללא פרמטר. הוא מחזיר מערך המכיל את כל האלמנטים ברשימה.
ניקח דוגמה נוספת להמרת רשימה למערך כדי להבין כיצד אנו יכולים להשתמש ב- toArray() שיטת הרשימה.
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;>