Recommended efficient methods for adding elements to Java arrays

Recommended efficient methods for adding elements to Java arrays

Arrays in Java are a very common and important data structure. Sometimes we need to add elements to an existing array Add elements. However, since the length of the array is fixed, adding directly to the array is not feasible. Therefore, we need to find an efficient way to add array elements. This article will introduce several common and efficient methods and provide corresponding code examples.

Method 1: Use the ArrayList class

ArrayList is a dynamic array class provided in Java, which can automatically adjust the size of the array as needed. ArrayList can be used to easily add array elements. The specific code is as follows:

// 创建一个ArrayList对象
ArrayList<Integer> list = new ArrayList<>();

// 添加元素
list.add(1);
list.add(2);
list.add(3);

// 打印数组
System.out.println("ArrayList: " + list);

Method 2: Use the Arrays.copyOf() method

The Arrays.copyOf() method can create a new array and copy all elements in the specified array into a new array. By specifying the length of the new array, we can achieve the effect of adding elements. The specific code is as follows:

// 原始数组
int[] arr = {1, 2, 3};

// 添加元素
arr = Arrays.copyOf(arr, arr.length + 1);
arr[arr.length - 1] = 4;

// 打印数组
System.out.println("Array: " + Arrays.toString(arr));

Method 3: Use the System.arraycopy() method

The System.arraycopy() method can copy the specified part of an array to another array. By specifying the length of the new array, we can achieve the effect of adding elements. The specific code is as follows:

// 原始数组
int[] arr = {1, 2, 3};

// 创建一个新数组
int[] newArr = new int[arr.length + 1];

// 复制原始数组的元素到新数组中
System.arraycopy(arr, 0, newArr, 0, arr.length);

// 添加元素
newArr[newArr.length - 1] = 4;

// 打印数组
System.out.println("Array: " + Arrays.toString(newArr));

Method 4: Use the Stream.concat() method

The Stream class was introduced in Java 8, which can easily operate on arrays. We can use the Stream.concat() method to construct a new Stream from the original array and the elements to be added, and convert it to an array. The specific code is as follows:

// 原始数组
Integer[] arr = {1, 2, 3};

// 要添加的元素
Integer elem = 4;

// 构造新的Stream
Integer[] newArr = Stream.concat(Arrays.stream(arr), Stream.of(elem))
                        .toArray(Integer[]::new);

// 打印数组
System.out.println("Array: " + Arrays.toString(newArr));

Summary:

This article introduces several efficient methods to add elements to Java arrays. Among them, using the ArrayList class is the simplest and most commonly used method, while using the Arrays.copyOf(), System.arraycopy() method and Stream.concat() method is more flexible and can provide better performance in specific situations. Based on actual needs, choosing the appropriate method can help us achieve more efficient array operations.

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