Java uses the asList() function of the Arrays class to convert an array into a List collection

Java uses the asList() function of the Arrays class to convert an array into a List collection

In Java programming, it is often necessary to convert an array into a collection for operation. Java provides a convenient and quick method: use the asList() function of the Arrays class to convert the array into a List collection. This article will introduce how to use the asList() function and provide code examples to help readers better understand.

The asList() function is a static method of the Arrays class. It accepts an array as a parameter and returns a List collection. Using the asList() function can quickly and easily convert an array into a List collection, eliminating the tedious steps of manually traversing the array.

The following is the method signature of the asList() function:

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

As shown above, the asList() function uses the syntax of variable parameters (varargs) and can accept any number of parameters. The parameter types must be consistent. It packs the received parameters into a list and returns this list.

The following is a simple example that shows how to use the asList() function to convert an integer array into a List collection:

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

public class ArrayToListExample {
    public static void main(String[] args) {
        // 声明一个整型数组
        Integer[] array = {1, 2, 3, 4, 5};

        // 将整型数组转换为List集合
        List<Integer> list = Arrays.asList(array);

        // 遍历List集合并打印元素
        for (Integer num : list) {
            System.out.println(num);
        }
    }
}

In the above code, we first declare an integer array array, and then use the asList() function to convert the array into a List collection and assign the result to the list variable. Finally, use an enhanced for loop to iterate through the list collection and print each element.

Note: The List collection converted using the asList() function is a fixed-length collection and does not support modification operations such as addition and deletion. If you try to modify the collection, an UnsupportedOperationException will be thrown. Therefore, if you need to modify the collection, it is recommended to copy the collection returned by asList() to a new List object.

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

public class ArrayToListExample {
    public static void main(String[] args) {
        // 声明一个整型数组
        Integer[] array = {1, 2, 3, 4, 5};

        // 将整型数组转换为List集合
        List<Integer> list = new ArrayList<>(Arrays.asList(array));

        // 向List集合中添加新元素
        list.add(6);
        list.add(7);

        // 打印List集合中的元素
        for (Integer num : list) {
            System.out.println(num);
        }
    }
}

In the above code, we use the constructor of ArrayList to create a new List object, and use the collection returned by the asList() function as the parameter of the constructor. In this way, an operable List collection is obtained, which can be added, deleted, and modified.

Summary:

Using the asList() function of the Arrays class can easily convert an array into a List collection, eliminating the trouble of manually traversing the array. However, it should be noted that the List collection returned by the asList() function is a fixed-length collection and does not support modification operations such as addition and deletion. If you need to modify the collection, you can first copy it to a new List object.

I hope the introduction in this article will be helpful to you in your daily Java development, and I wish you happy programming!

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