Filling the elements of an array using the fill() method of the Arrays class in Java

Use the fill() method of the Arrays class in Java to fill the elements of the array

In Java, we often need to operate and modify arrays. One of the common needs is to fill the elements of an array. Java provides the fill() method of the Arrays class to achieve this purpose. This article will introduce in detail how to use the fill() method of the Arrays class to fill the elements of an array, and provide code examples to demonstrate.

Before using the fill() method of the Arrays class, we need to create an array first. The following is a simple example that shows the process of creating an integer array:

int[] numbers = new int[5];

The above code creates an integer array of length 5 with an initial value of 0. Now we can use the fill() method to fill the elements of the array. The syntax of the fill() method is as follows:

public static void fill(Object[] a, Object val)

where a is the array to be filled, and val is the value to be filled. Note that the filled value must match the type of the array element. The following is an example of filling an array using the fill() method:

import java.util.Arrays;

public class ArrayFillExample {
    public static void main(String[] args) {
        int[] numbers = new int[5];
        Arrays.fill(numbers, 10);
        for (int number : numbers) {
            System.out.println(number);
        }
    }
}

In the above example, we first created an integer array numbers of size 5. Then use the fill() method to fill all elements of the array numbers to 10. Finally use a for-each loop to iterate through the array and print each element.

Run the above code, we will see that the output is:

10
10
10
10
10

As expected, all elements of the array numbers are filled with 10.

In addition to filling integer arrays, we can also use the fill() method to fill other types of arrays, such as string arrays. The following is an example of filling a string array using the fill() method:

import java.util.Arrays;

public class ArrayFillExample {
    public static void main(String[] args) {
        String[] names = new String[3];
        Arrays.fill(names, "John");
        for (String name : names) {
            System.out.println(name);
        }
    }
}

In the above example, we first created a string array names of size 3. Then use the fill() method to fill all elements of the array names with "John". Finally use a for-each loop to iterate through the array and print each element.

Run the above code, we will see that the output is:

John
John
John

Similarly, all elements of the string array names are filled with "John".

In addition to filling the entire array, we can also use the fill() method to fill a specified range of the array. The fill() method has two overloaded forms, one of which allows us to specify the starting position and ending position of the filling. The following is an example of using the fill() method to fill a specified range of an array:

import java.util.Arrays;

public class ArrayFillExample {
    public static void main(String[] args) {
        int[] numbers = new int[5];
        Arrays.fill(numbers, 1, 4, 5);
        for (int number : numbers) {
            System.out.println(number);
        }
    }
}

In the above example, we first created an integer array numbers of size 5. Then use the fill() method to fill the elements at index positions from 1 to 4 (excluding index 4) of the array numbers to 5. Finally use a for-each loop to iterate through the array and print each element.

Run the above code, we will see that the output is:

0
5
5
5
0

As expected, the elements at index positions from 1 to 4 of the array numbers are successfully filled with 5.

Summary:
This article introduces the use of the fill() method of the Arrays class in Java to fill the elements of the array. We can use the fill() method to fill the entire array or elements within a specified range. When using the fill() method, it is important to note that the filled value must match the type of the array element. I hope the content of this article will be helpful to learn and understand how to fill the elements of an array in Java.

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