Chapter 8: Problem 24

How do you insert an item at a specific location in an ArrayList object?

Short Answer

Expert verified

**Answer:** To insert an element into an ArrayList at a specific index, you can use the `add()` method with two parameters: the index at which to insert the element and the element itself. For example, if you have an ArrayList named `namesList` and want to insert the element "Cathy" at index 1, you can use the following code: `namesList.add(1, "Cathy");`.

Step by step solution

Define an ArrayList

An ArrayList is a dynamic array in Java, which allows us to store and manipulate a collection of elements. It can grow and shrink its size as needed during runtime. The ArrayList class is a part of the java.util package and provides numerous methods to work with the elements within it.

Create an ArrayList object and populate it with sample data

First, let's import the necessary package and create an ArrayList object containing some sample data: ```java import java.util.ArrayList; public class Main { public static void main(String[] args) { ArrayList namesList = new ArrayList(); namesList.add("John"); namesList.add("Alice"); namesList.add("Bob"); } } ``` In this example, we have created an ArrayList of strings called `namesList` and populated it with three names (John, Alice, and Bob).

Insert an element at a specified index using the add method

Now, let's insert a new name, "Cathy", at index 1, using the `add` method: ```java namesList.add(1, "Cathy"); ``` This line of code tells the ArrayList to insert the element "Cathy" at the specified index (1), moving the elements that come after it one position forward.

Verify the result

To confirm that our name has been inserted into the ArrayList correctly, we can print the contents of the updated ArrayList: ```java System.out.println(namesList); ``` After running the program, we should see the following output: ``` [John, Cathy, Alice, Bob] ``` This verifies that our element "Cathy" has been successfully inserted at index 1 as desired.

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How do you insert an item at a specific location in an ArrayList object?

Short Answer

Step by step solution

Define an ArrayList

Create an ArrayList object and populate it with sample data

Insert an element at a specified index using the add method

Verify the result

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