Convert an array to a list using the asList() method of the Arrays class in Java

Use the asList() method of the Arrays class in Java to convert an array into a list

In Java programming, you often encounter the need to convert an array into a list. Java provides an asList() method of the Arrays class, which can easily convert arrays into lists. This article explains how to use the asList() method and provides code examples to demonstrate it.

First, let us understand the definition and function of the asList() method. The asList() method is a static method of the Arrays class, which is defined as follows:

public static <T> List<T> asList(T... a)

It accepts a variable-length parameter and converts it into a list object. We can pass an array of any type to the asList() method and it will return a list of the corresponding type. This way, we can operate on arrays just like lists.

The following is a simple example that demonstrates how to convert an integer array into a list and operate on it:

import java.util.Arrays;
import java.util.List;

public class ArrayToListExample {
    public static void main(String[] args) {
        // 定义一个整型数组
        Integer[] array = {1, 2, 3, 4, 5};
        
        // 将数组转换为列表
        List<Integer> list = Arrays.asList(array);
        
        // 输出列表中的元素
        for (Integer num : list) {
            System.out.println(num);
        }
        
        // 修改列表中的元素
        list.set(0, 10);
        
        // 输出修改后的数组
        System.out.println(Arrays.toString(array));
    }
}

The above code first defines an integer array and assigns it to {1, 2, 3, 4, 5}. Then, convert the array to a list through the Arrays.asList() method and assign the returned list to the list variable. Next, use an enhanced for loop to iterate through the list and output each element in it. Finally, modify the first element in the list to 10 by calling the list.set() method, and output the modified array through the Arrays.toString() method.

Run the above example code, the following results will be output:

1
2
3
4
5
[10, 2, 3, 4, 5]

As you can see from the output results, after converting the array into a list, we can use the list to operate the array. When we modify an element in the list, the corresponding array is also modified.

It should be noted that the asList() method returns a fixed-size list, which means that we cannot add or delete elements to the list. If we try to do this, an UnsupportedOperationException will be thrown.

If we want to get a list that can be added or deleted, we can achieve this by constructing an ArrayList object. The following is a sample code:

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class ArrayToListExample {
    public static void main(String[] args) {
        // 定义一个整型数组
        Integer[] array = {1, 2, 3, 4, 5};
        
        // 将数组转换为列表
        List<Integer> list = new ArrayList<>(Arrays.asList(array));
        
        // 输出列表中的元素
        for (Integer num : list) {
            System.out.println(num);
        }
        
        // 添加元素到列表
        list.add(6);
        
        // 输出修改后的列表
        System.out.println(list);
    }
}

The above code uses the ArrayList constructor and takes the list returned by the Arrays.asList() method as a parameter when converting the array to a list. In this way, we get a list that can be added or deleted.

In this article, we introduced how to convert an array into a list using the asList() method of the Arrays class. In this way, we can easily operate arrays in Java programming just like operating lists. Whether it is simply traversing the elements of the list or modifying an element in the list, we can easily achieve it through the asList() method. However, it should be noted that the asList() method returns a fixed-size list and does not support adding or deleting elements. If you need to modify the list, you can do so by constructing an ArrayList object. I hope this article helped you understand how arrays are converted to lists in Java.

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