CCF 碰撞的小球 java 100分

package ccf第二題;
import java.util.Scanner;
public class 碰撞的小球 {
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();
		int L = in.nextInt();
		int t = in.nextInt();
		Ball[] balls = new Ball[n];
		for (int i = 0; i < n; i++) {
			balls[i] = new Ball(in.nextInt(), 1);
		}
		for (int i = 0; i < t; i++) {
			//所有小球向前走一格
			for (int j = 0; j < balls.length; j++) {
				int endj = balls[j].start + balls[j].v;
				balls[j].start = endj;
			}
			for (int j = 0; j < n;j++ ) { // 小球j
				if (balls[j].start == 0) {// 撞左牆
					balls[j].v = -1 * balls[j].v;
				}
				if (balls[j].start == L) {// 撞右牆
					balls[j].v = -1 * balls[j].v;
				}				
				for (int k = j+1; k < n; k++) {
					if (balls[k].start == balls[j].start) { // 兩小球碰撞
						balls[j].v = -1 * balls[j].v;
						balls[k].v = -1 * balls[k].v;
					}
				}
			}
		}
		in.close();
		for (int i = 0; i < balls.length; i++) {
			System.out.print(balls[i].start + " ");
		}
	}
	static class Ball {
		int start;
		int v;

		public Ball(int start, int v) {
			this.start = start;
			this.v = v;
		}
	}
}