YouTipJava Arraylist
[ Java Collections Framework](#)
ArrayList class is a dynamically modifiable array, unlike ordinary arrays, it has no fixed size limit, we can add or delete elements.
ArrayList inherits AbstractList and implements the List interface.
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The ArrayList class is in the java.util package and needs to be imported before use. The syntax is as follows:
import java.util.ArrayList; // Import ArrayList ClassArrayList objectName =new ArrayList(); // Initialization
* **E**: Generic data type, used to set the data type of objectName, **can only be a reference data type**.
* **objectName**: Object name.
ArrayList is an array queue, providing related add, delete, modify, traverse and other functions.
### Adding Elements
ArrayList class provides many useful methods, to add elements to ArrayList you can use the add() method:
## Example
import java.util.ArrayList;
public class TutorialTest {
public static void main(String[] args){
ArrayList sites =new ArrayList();
sites.add("Google");
sites.add("Tutorial");
sites.add("Taobao");
sites.add("Weibo");
System.out.println(sites);
}
}
In the above example, the output is:
[Google, Tutorial, Taobao, Weibo]
### Accessing Elements
To access elements in ArrayList, you can use the get() method:
## Example
import java.util.ArrayList;
public class TutorialTest {
public static void main(String[] args){
ArrayList sites =new ArrayList();
sites.add("Google");
sites.add("Tutorial");
sites.add("Taobao");
sites.add("Weibo");
System.out.println(sites.get(1));// Access the second element
}
}
**Note**: Array index values start from 0.
In the above example, the output is:
Tutorial
### Modifying Elements
To modify elements in ArrayList, you can use the set() method. The set(int index, E element) method's first parameter is the index, indicating the position of the element to replace, and the second parameter is the new element (element), indicating the new value to set:
## Example
import java.util.ArrayList;
public class TutorialTest {
public static void main(String[] args){
ArrayList sites =new ArrayList();
sites.add("Google");
sites.add("Tutorial");
sites.add("Taobao");
sites.add("Weibo");
sites.set(2, "Wiki");// The first parameter is the index position, and the second is the value to be modified
System.out.println(sites);
}
}
In the above example, the output is:
[Google, Tutorial, Wiki, Weibo]
### Deleting Elements
To delete elements in ArrayList, you can use the remove() method:
## Example
import java.util.ArrayList;
public class TutorialTest {
public static void main(String[] args){
ArrayList sites =new ArrayList();
sites.add("Google");
sites.add("Tutorial");
sites.add("Taobao");
sites.add("Weibo");
sites.remove(3);// Remove the fourth element
System.out.println(sites);
}
}
In the above example, the output is:
[Google, Tutorial, Taobao]
### Calculating Size
To calculate the number of elements in ArrayList, you can use the size() method:
## Example
import java.util.ArrayList;
public class TutorialTest {
public static void main(String[] args){
ArrayList sites =new ArrayList();
sites.add("Google");
sites.add("Tutorial");
sites.add("Taobao");
sites.add("Weibo");
System.out.println(sites.size());
}
}
In the above example, the output is:
4
### Iterating Through ArrayList
We can use for to iterate through elements in the ArrayList:
## Example
import java.util.ArrayList;
public class TutorialTest {
public static void main(String[] args){
ArrayList sites =new ArrayList();
sites.add("Google");
sites.add("Tutorial");
sites.add("Taobao");
sites.add("Weibo");
for(int i =0; i < sites.size(); i++){
System.out.println(sites.get(i));
}
}
}
In the above example, the output is:
GoogleTutorialTaobaoWeibo
You can also use for-each to iterate through elements:
## Example
import java.util.ArrayList;
public class TutorialTest {
public