Computer Networking: A Top-Down Approach (7th Edition)
7th Edition
ISBN: 9780133594140
Author: James Kurose, Keith Ross
Publisher: PEARSON
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![### Java For-Loops and ArrayLists
Let's examine the for-loops in the given Java program and discuss how to handle them when working with an `ArrayList`.
**Java Program:**
```java
public class BasicArray {
public static void main(String[] args) {
int[] basic = new int[4];
for (int i = 0; i < basic.length; i++) {
basic[i] = i + 1;
}
for (int i = 0; i < basic.length; i++) {
basic[i] = basic[i] * 5;
}
for (int i = 0; i < basic.length; i++) {
System.out.println(basic[i]);
}
}
}
```
#### Questions:
**a) Which ArrayList method should you use to control the for-loop iterations?**
To control the iterations of a for-loop when using an `ArrayList`, you should use the `size()` method. This method returns the number of elements in the `ArrayList`, which you can then use as the loop's endpoint.
**Example:**
```java
ArrayList<Integer> arrayList = new ArrayList<>();
for (int i = 0; i < arrayList.size(); i++) {
// Loop body
}
```
**b) Explain why the first for-loop cannot be controlled by that ArrayList method (but the other two for-loops can).**
The first for-loop cannot be controlled by the `size()` method because it initializes the array and assigns values to its elements. When you replace the array with an `ArrayList`, you must use the `add` method to add elements to the `ArrayList`. The size of the `ArrayList` would be zero initially, and using the `size()` method in the first loop would result in no iterations.
**Example Modification:**
- Replace `int[] basic = new int[4];` with `ArrayList<Integer> basic = new ArrayList<>();`.
- Use the `add` method to add elements in the first loop.
```java
for (int i = 0; i < 4; i++) {
basic.add(i + 1);
}
```
**Quick Review of Array Access and Modification in Java:**
| Method (Parameters) | Return Value Type | Description |
|--------------------------------|-------------------|---------------------------------------------------------------|
| `add(E element)`](https://content.bartleby.com/qna-images/question/6cf78908-a1f9-4330-9ece-f4021df10613/0ed2db06-cbf1-49a2-b038-d5abcc012bd5/j76opsb_processed.png)
Transcribed Image Text:### Java For-Loops and ArrayLists
Let's examine the for-loops in the given Java program and discuss how to handle them when working with an `ArrayList`.
**Java Program:**
```java
public class BasicArray {
public static void main(String[] args) {
int[] basic = new int[4];
for (int i = 0; i < basic.length; i++) {
basic[i] = i + 1;
}
for (int i = 0; i < basic.length; i++) {
basic[i] = basic[i] * 5;
}
for (int i = 0; i < basic.length; i++) {
System.out.println(basic[i]);
}
}
}
```
#### Questions:
**a) Which ArrayList method should you use to control the for-loop iterations?**
To control the iterations of a for-loop when using an `ArrayList`, you should use the `size()` method. This method returns the number of elements in the `ArrayList`, which you can then use as the loop's endpoint.
**Example:**
```java
ArrayList<Integer> arrayList = new ArrayList<>();
for (int i = 0; i < arrayList.size(); i++) {
// Loop body
}
```
**b) Explain why the first for-loop cannot be controlled by that ArrayList method (but the other two for-loops can).**
The first for-loop cannot be controlled by the `size()` method because it initializes the array and assigns values to its elements. When you replace the array with an `ArrayList`, you must use the `add` method to add elements to the `ArrayList`. The size of the `ArrayList` would be zero initially, and using the `size()` method in the first loop would result in no iterations.
**Example Modification:**
- Replace `int[] basic = new int[4];` with `ArrayList<Integer> basic = new ArrayList<>();`.
- Use the `add` method to add elements in the first loop.
```java
for (int i = 0; i < 4; i++) {
basic.add(i + 1);
}
```
**Quick Review of Array Access and Modification in Java:**
| Method (Parameters) | Return Value Type | Description |
|--------------------------------|-------------------|---------------------------------------------------------------|
| `add(E element)`
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