Java中仅用一个分号实现int数组旋转的技术问询

First, let's break down the problem: your original rotateByN uses nested loops that introduce multiple semicolons, and we need to trim that down to exactly one semicolon in the method body. Here's a working solution that keeps the core functionality intact while meeting the requirement:

public class Four {
    static void rotateOnce(int[] in) {
        int tmp = in[0];
        for (int i = 1; i < in.length; i++) in[i - 1] = in[i];
        in[in.length - 1] = tmp;
    }

    static void rotateByN(int[] in, int n) {
        n > 0 ? (rotateOnce(in), rotateByN(in, n - 1)) : null;
    }

    public static void main(String[] args) {
        int[] arr = { 2, 7, 6, 1, 0 };
        rotateByN(arr, 3);
        for (int r : arr) System.out.println(r);
    }
}

How This Works #

1. Extract Single Rotation Logic: We move the step of rotating the array by 1 position into a separate rotateOnce method. This isolates the loop-based logic and cleans up the rotateByN method we need to simplify.
2. Recursion + Ternary + Comma Operator: Instead of using a for loop to repeat rotations n times, we use recursion. The ternary operator checks if we still need to perform rotations (n > 0). If true, we use the comma operator to first execute rotateOnce(in) and then recurse with n-1. This entire logic fits into a single line, which only requires one semicolon.
3. Preserve Original Behavior: This approach does exactly what your original code does—rotates the array n steps by shifting the first element to the end each time—while modifying the input array directly (no new array created).

Test Output #

Running the main method will produce the same result as your original code:

1
0
2
7
6

内容的提问来源于stack exchange，提问作者hwgn