How to reverse array in Java? 2 ways to reverse arrays in Java (code examples)

Array operation How to reverse the output of a Java array? The following article will introduce to you two simple methods to achieve array reversal in Java. It has certain reference value and I hope it will be helpful to everyone. [Video tutorial recommendation: java tutorial]

Method 1: Use a loop to exchange the positions of elements in the array

Use a loop to exchange the positions of elements in the original array: the first element is exchanged with the last element, the second element is exchanged with the last element, and so on until the end.

For example, in the array [1,2,3,...,n-2,n-1,n], we can exchange 1 and n, and 2 and n-1, 3 and n-2 are exchanged.

Implementation code

public class arrayReverse { 
  
    /*数组中元素位置进行交换*/
    static void reverse(int a[], int n) 
    { 
        int i, k, t; 
        for (i = 0; i < n / 2; i++) { 
            t = a[i]; 
            a[i] = a[n - i - 1]; 
            a[n - i - 1] = t; 
        } 
  
        /*printing the reversed array*/
        System.out.println("\n反转数组是:"); 
        for (k = 0; k < n; k++) { 
            System.out.println(a[k]); 
        } 
    } 
  
    public static void main(String[] args) 
    { 
        int [] arr = {5, 6, 7, 8, 9}; 
        System.out.println("原数组是: "); 
        for (int k = 0; k < arr.length; k++) { 
            System.out.println(arr[k]); 
        } 
        reverse(arr, arr.length); 
    } 
}

Output:

原数组是: 
5
6
7
8
9

反转数组是:
9
8
7
6
5

Method 2: Use a loop to reversely place the original array elements in the new array

Inside the function, initialize a new array (the size of the array is the same as the first array arr). The array arr[] is iterated from the first element, placing each element in it in the new array from behind, i.e. iterating the new array from the last element. This way, all elements of the array arr[] will be placed in the new array in reverse order. We then iterate over the new array from scratch and output the elements of the array.

Implementation code:

public class reverseArray { 
  
    /* 反转数组并将其存储在另一个数组中的函数*/
    static void reverse(int a[], int n) 
    { 
        int[] b = new int[n]; 
        int j = n; 
        for (int i = 0; i < n; i++) { 
            b[j - 1] = a[i]; 
            j = j - 1; 
        } 
  
        /*输出反转数组*/
        System.out.println(" \n反转数组是: "); 
        for (int k = 0; k < n; k++) { 
            System.out.println(b[k]); 
        } 
    } 
  
    public static void main(String[] args) 
    { 
        int [] arr = {10, 20, 30, 40, 50}; 
System.out.println("原数组是: "); 
for (int k = 0; k < arr.length; k++) { 
            System.out.println(arr[k]); 
        } 
        reverse(arr, arr.length); 
    } 
}

Output:

原数组是: 
10
20
30
40
50
 
反转数组是: 
50
40
30
20
10

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