java - Java 中的随机数问题

Question

我编写了一段代码，用 Java 随机方向移动对象。有两个功能。

1. FindRandomDirection - 从 8 个可能的方向中获取随机方向(方向由数字键盘中的数字 1、2、3、4、6、7、8、9 表示)。检查对象是否靠近任何边界。如果是这样，该对象将向远离边界的方向移动。

2. MoveObject - 通过移动恒定的 STEP 来更改对象的 (X, Y) 坐标。

但是我给 X、Y 的值是多少？重复该过程几次(700或更多)后，X、Y的值变为{X:20-50}和{Y:450-465}。

即

Case 1: (x:35,y:65) becomes (x:35, y:465)
Case 2: (x:30, y:455) becomes (x:30, y:460)
Case 3: (x:435, y:65) becomes (x:25, y:460)
Case 4: (x:430, y:465) becomes (x:40, y:460)

我想知道为什么在几次迭代之后 x、y 点会收敛到这些值，即使我随机生成数字。

下面是相同的代码。

import java.io.*;
public class bug
{
    //public static int x = 35;
    //public static int y = 60;

    //public static int x = 35;
    //public static int y = 460;

    //public static int x = 435;
    //public static int y = 60;

    public static int x = 435;
    public static int y = 460;

    public static final int NORTH = 8;
    public static final int EAST = 6;
    public static final int WEST = 4;
    public static final int SOUTH = 2;
    public static final int NORTHEAST = 9;
    public static final int NORTHWEST = 7;
    public static final int SOUTHWEST = 1;
    public static final int SOUTHEAST = 3;
    public static final int STEP = 5;

    //Function to move the object in a specified direction.
    public static void moveObject(int direction)
    {
            double nX = 0, nY=0;
            switch(direction)
            {
            case  NORTH:
                nY = y- STEP; 
                nX = x;
                break;
            case  SOUTH:
                nY = y+ STEP; 
                nX = x;
                break;
            case  EAST:             
                nY = y; 
                nX = x +  STEP;
                break;
            case  WEST:
                nY = y; 
                nX = x- STEP;               
                break;
            case  NORTHEAST:
                nX = x +  STEP;
                nY = y- STEP; 
                break;
            case  NORTHWEST:
                nX = x- STEP;
                nY = y- STEP; 
                break;
            case  SOUTHEAST:
                nX = x +  STEP;
                nY = y+ STEP; 
                break;
            case  SOUTHWEST:
                nX = x- STEP;
                nY = y+ STEP; 
                break;
            }
            x = (int) nX;
            y = (int) nY;
            System.out.println("Direction: "+direction+"; X: "+x+"; Y: "+y);
        }
//Function to move the object in a random direction
//Also if wall(Border) is present the object should move in proper direction
    public static int findRandomDirection(int objObjectX, int objObjectY)
    {
        int[] move = {1,2,3,4,0,6,7,8,9};
        int randDir=0;
        //Generate a random direction to move. Generate new direction if the objected can not be moved in a direction 
        do
        {
            java.util.Random randomGenerator = new java.util.Random();
            randDir = randomGenerator.nextInt(8);

            //If the object lies near East Border, it can not move in that direction
            if(objObjectX <= 25)
            {
                move[0] = 0;
                move[3] = 0;
                move[6] = 0;
            }

            //If the object lies near West Border, it can not move in that direction
            if(objObjectX >= 465)
            {
                move[2] = 0;
                move[5] = 0;
                move[8] = 0;                
            }

            //If the object lies near North Border, it can not move in that direction
            if(objObjectY <= 25)
            {
                move[6] = 0;
                move[7] = 0;
                move[8] = 0;
            }

            //If the object lies near South Border, it can not move in that direction
            if(objObjectY >= 465)
            {
                move[0] = 0;
                move[1] = 0;
                move[2] = 0;                
            }
        } while(move[randDir]==0);
        return move[randDir];       
    }
    public static void main(String[] args)
    {
        for(int i = 0; i<1000;i++)
        {
        int dir=findRandomDirection(x,y);   
        moveObject(dir);
        }
    }
}

随着时间的推移，我的物体会移向棋盘的左下角。请帮助我找到错误。

Answer 1

由于您使用的是 nextInt(8)，因此返回的值将始终在 0 到 7 之间(含)。由于 8 永远不会返回，因此移动会偏向相反的方向。您可能想要使用 nextInt(9) 返回 0 到 8(含)之间的值。

编辑:澄清一下，由于永远不会选择“8”作为随机方向，并且移动[8]==9，因此该对象永远不会在东北中移动方向，这意味着随着时间的推移，它将倾向于向西南移动。

此外，正如 @Joey 上面所说，您不应该每次都重新初始化 Random 对象，但这并不是导致漂移行为的原因。