What are the ways to dynamically add elements to a Java array?

Java array is a data structure used to store fixed-size elements of the same type. When creating an array, you need to specify the length of the array, which means the size of the array is fixed. However, in actual programming, sometimes it is necessary to dynamically add elements to an array. This article will introduce how to dynamically add elements to an array in Java and provide code examples.

In Java, there are several common methods for dynamically adding elements to an array:

1. Using the ArrayList class
   ArrayList is a class in the Java collection framework, which provides Convenient way to add elements dynamically. We can declare an ArrayList object and then add elements to it using the add() method. ArrayList automatically adjusts the array size and reallocates elements.

The following is a code example using ArrayList:

import java.util.ArrayList;

public class DynamicArray {
    public static void main(String[] args) {
        // 创建ArrayList对象
        ArrayList<Integer> numbers = new ArrayList<Integer>();

        // 向ArrayList添加元素
        numbers.add(1);
        numbers.add(2);
        numbers.add(3);

        // 遍历并打印ArrayList中的元素
        for (int i = 0; i < numbers.size(); i++) {
            System.out.println(numbers.get(i));
        }
    }
}

2. Create a new array
   If you don’t want to use ArrayList, you can also manually create a new array to achieve dynamics Add effects to elements. First, create an array of initial size. When you need to add a new element, create a new array larger than the original array, copy the elements in the original array to the new array, and then add the new elements to the end of the new array.

The following is a code example using a new array:

public class DynamicArray {
    public static void main(String[] args) {
        // 创建原数组
        int[] numbers = new int[3];

        // 添加元素到原数组
        numbers[0] = 1;
        numbers[1] = 2;
        numbers[2] = 3;

        // 创建新数组，大小比原数组大一
        int[] newNumbers = new int[numbers.length + 1];

        // 将原数组中的元素复制到新数组中
        for (int i = 0; i < numbers.length; i++) {
            newNumbers[i] = numbers[i];
        }

        // 添加新元素到新数组末尾
        newNumbers[numbers.length] = 4;

        // 遍历并打印新数组中的元素
        for (int i = 0; i < newNumbers.length; i++) {
            System.out.println(newNumbers[i]);
        }
    }
}

Through the ArrayList class or manually creating a new array, we can implement the function of dynamically adding elements to an array in Java. These methods provide flexibility and convenience and can be selected and used according to actual needs.

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