Question

How to reverse an int array in Java

Answer 1

import java.util.Arrays;

public class MyClass {
    static void reverseIntArray(int array[]) {
        int left = 0, right = array.length - 1;
        
        while (left < right) {
            int temp = array[left];
            array[left] = array[right];
            array[right] = temp;

            left++;
            right--;
        }
    }
    
    public static void main(String args[]) {
        int[] array = {1, 2, 3, 4, 5, 6};

        reverseIntArray(array);
        
        System.out.println(Arrays.toString(array));
    }
}
    
   
   
    
/*
run:
   
[6, 5, 4, 3, 2, 1]
 
*/

 

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Answer 2

import java.util.stream.Collectors;
import java.util.Collections;
import java.util.Arrays;
import java.util.List;

public class MyClass {

    public static void main(String args[]) {
        int[] array = {1, 2, 3, 4, 5, 6};

        List<Integer> list = Arrays.stream(array).boxed().collect(Collectors.toList());

        Collections.reverse(list);

        array = list.stream().mapToInt(i -> i).toArray();
        
        System.out.println(Arrays.toString(array)); 
    }
}
    
   
   
    
/*
run:
   
[6, 5, 4, 3, 2, 1]
 
*/

 

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