ArrayList empty
The syntax of the isEmpty() method is: Show
Here, arraylist is an object of the ArrayList class. isEmpty() ParametersThe isEmpty() method does not take any parameters. isEmpty() Return Value
Example: Check if ArrayList is Emptyimport java.util.ArrayList; class Main { public static void main(String[] args) { // create an ArrayList ArrayListOutput Newly Created ArrayList: [] Is the ArrayList empty? true Updated ArrayList: [Python, Java] Is the ArrayList empty? falseIn the above example, we have created a arraylist named languages. Here, we have used the isEmpty() method to check whether the arraylist contains any elements or not. Initially, the newly created arraylist does not contain any element. Hence, isEmpty() returns true. However, after adding some elements (Python, Java), the method returns false. Learn to clear arraylist or empty an arraylist in Java. Clearing a list means to remove all elements from the list. It is same as reset the list to it’s initial state when it has no element stored in it. To clear an arraylist in java, we can make use of two methods.
Both methods will finally empty the list. But there is a difference in how they perform the empty operation. 1. Clear arraylist with ArrayList.clear()Java program to clear an arraylist. import java.util.ArrayList; import java.util.Arrays; public class ArrayListExample { public static void main(String[] args) throws Exception { ArrayListProgram output. [a, b, c, d, e] []2. Clear arraylist with ArrayList.removeAll()Java program to remove all elements of an arraylist with removeAll() method. Program output. [a, b, c, d, e] []3. Difference between clear() vs removeAll() methodsAs I said before, both methods empty an list. But difference lies in how they make list clear. Let’s see the code for both methods to understand the actions they perform.
4. ConclusionBy going through the sourcecode of both methods, we can safely say that clear() method give much better performance because of less number of statements it executes. removeAll() method lack in performance because of extra call to contains() method. But, still removeAll() method is useful in cases such as merge two arraylists without duplicate elements. Happy Learning !! Read More: A Guide to Java ArrayList Let us know if you liked the post. That’s the only way we can improve. ArrayList clear() method is used to removes all of the elements from the list. The list will be empty after this call returns. 1. ArrayList clear() syntaxclear() method does simple thing. It iterates the backing array inside arraylist and assign all elements 'null' value and set the size attribute to '0'. public void clear() { modCount++; // clear to let GC do its work for (int i = 0; i < size; i++) elementData[i] = null; size = 0; }
2. ArrayList clear() exampleJava program to make empty an arraylist using clear() method. import java.util.ArrayList; public class ArrayListExample { public static void main(String[] args) { ArrayListProgram output. [A, B, C, D] []3. ArrayList clear vs newAn empty arraylist has zero elements. A new arraylist also has zero elements. But there is differenece between them. The difference between an empty and a new arraylist is the size of backing array. As clear() method does not resize the backing array, so after clear method you may have a list which has backing array of a larger size (if list was pretty big before clear() method was called). Except above difference in capacity, there is no difference between both kind of lists. Happy Learning !! Read More: A Guide to Java ArrayList Let us know if you liked the post. That’s the only way we can improve.
To create an Empty ArrayList in Java, you can use new keyword and ArrayList constructor with no arguments passed to it. Following is the syntax to create an empty ArrayList. ArrayList
Example 1 – Create an Empty ArrayList of StringsIn the following example, we shall create an empty ArrayList of Strings. Java Program import java.util.ArrayList; public class ArrayListExample { public static void main(String[] args) { ArrayListnames is an empty ArrayList that can store String elements. Example 2 – Create an Empty ArrayList of ObjectsIn the following example, we shall create an empty ArrayList that can store Car type objects. Java Program import java.util.ArrayList; public class ArrayListExample { public static void main(String[] args) { ArrayListcars is an empty ArrayList that can store Car objects. ConclusionIn this Java Tutorial, we have learned how to create an empty ArrayList in Java. Test your Java Basics with our Java Quiz ➥ PDF Download - How to Create an Empty ArrayList in Java?isEmpty() method of java.util.ArrayList class is used for checking whether the list is empty or not. This method returns a boolean value. public boolean isEmpty() It returns true if the list is empty otherwise it gives false. Examplepackage beginnersbook.com; import java.util.ArrayList; public class IsEmptyExample { public static void main(String args[]) { //ArrayList of Integer Type ArrayListOutput: Is ArrayList Empty: true Is ArrayList Empty: false 1 88 9 17 |