Using the copyOf() method of the Arrays class in Java to copy part of an array

Use the copyOf() method of the Arrays class in Java to copy part of the contents of the array

In Java, when we need to copy part of the contents of the array, we often use the copyOf() method of the Arrays class. This method can help us simplify the code and realize the copy operation of the array.

The Arrays class is a tool class provided by Java. It contains many static methods for operating arrays. Among them, the copyOf() method can copy the contents of a source array to a new array according to the specified length and return the new array.

The syntax of the copyOf() method is as follows:

public static <T> T[] copyOf(T[] original, int newLength)

where original represents the source array to be copied, and newLength represents the length of the new array.

Next, let us use a simple example to demonstrate how to use the copyOf() method to copy part of the array.

Suppose we have an integer array arr, as shown below:

int[] arr = {1, 2, 3, 4, 5};

Now, we want to copy the first three elements of the arr array to a new array. You can use the copyOf() method to achieve this function. The code is as follows:

import java.util.Arrays;

public class CopyArrayExample {
    public static void main(String[] args) {
        int[] arr = {1, 2, 3, 4, 5};

        int[] newArr = Arrays.copyOf(arr, 3);

        System.out.println("原始数组：");
        for (int i : arr) {
            System.out.print(i + " ");
        }

        System.out.println("
新数组：");
        for (int i : newArr) {
            System.out.print(i + " ");
        }
    }
}

Run the above code and the output result is as follows:

原始数组：
1 2 3 4 5
新数组：
1 2 3

Through the Arrays.copyOf() method, we successfully copy the original array arr The first three elements of are copied to the new array newArr.

It should be noted that when the copyOf() method copies an array, it will only copy the elements of the specified length. The excess elements will be truncated or filled with default values ​​(for example, integer arrays are filled with 0 by default). In the above example, we copied the first three elements of the original array arr into the new array, so the new array contains only 3 elements.

In addition, the copyOf() method can also be used to copy other types of arrays, such as string arrays, floating point arrays, etc. Just replace the type of the original array with the corresponding type.

To summarize, through the copyOf() method of the Arrays class in Java, we can easily copy part of the array. This method is simple and easy to use, and can help us improve the readability and efficiency of the code. If you encounter the need to copy an array in daily Java development, remember to try to use the copyOf() method to achieve it!

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