Question

所以给定一个数组的元素，我试图创建一个Location对象的arraylist，其中包含与给定位置相邻的所有元素（对角线和旁边，但不包括给定的位置）。这是我的位置课程：

public class Location
{
// Row and column positions.
private int row;
private int col;


public Location(int row, int col)
{
    this.row = row;
    this.col = col;

}
//getRow() & getCol() methods not shown

以下是我试图在另一个类中完成的方法：

public List<Location> adjacentLocations(Location location)
{
    List<Location> locations = new ArrayList<>();
    //todo, diag, next

    return locations
}

Answer 1

为什么不直接将列表指定为ArrayList。例如：

 ArrayList<Location> locations = new ArrayList<>();

public ArrayList<Location> adjacentLocations(Location location)
{
    locations.add(location);
}

public ArrayList<Location> getLocations()
{
    for(int i = 0; i < locations.length; i++)
    {
        System.out.println(locations[i]);
    }
}

Answer 2

我假设有负坐标是无效的。

public List<Location> adjacentLocations(Location location)
{
    List<Location> locations = new ArrayList<Location>();

    // Calculate all the adjacent positions relative to the specified point.
    int row = location.getRow();
    int col = location.getCol();
    for (int r = row -1; r<row +2; r++)
    {
        for (int c = col -1; c < col + 2; c++)
        {
            if ((c > -1 && r > -1) && !(r == row && c == col)) 
            {
                locations.add(new Location(r, c));
            }
        }
    }

    return locations;
}

填写课程以证明用法：

package stacktest;

import java.util.ArrayList;
import java.util.List;

public class Location {

    // Row and column positions.
    private int row;
    private int col;

    public Location(int row, int col)
    {
        this.row = row;
        this.col = col;

    }

    public int getRow()
    {
        return this.row;
    }

    public int getCol()
    {
        return this.col;
    }

    public String toString()
    {
        return "[" + row + ", " + col + "]";
    }

    public List<Location> adjacentLocations()
    {
        List<Location> locations = new ArrayList<Location>();

        // Calculate all the adjacent positions relative to the specified point.
        for (int r = row -1; r<row +2; r++)
        {
            for (int c = col -1; c < col + 2; c++)
            {
                if ((c > -1 && r > -1) && !(r == row && c == col)) 
                {
                    locations.add(new Location(r, c));
                }
            }
        }

        return locations;
    }

    public static void main(String[] args)
    {
        ArrayList<Location> originalLocations = new ArrayList<Location>();
        originalLocations.add(new Location(4, 10));
        originalLocations.add(new Location(100, 100));
        originalLocations.add(new Location(1, 0));

        for (Location l: originalLocations)
        {
            List<Location> adjacent = l.adjacentLocations();
            System.out.println("orig: " + l);
            for (Location adj: adjacent)
            {
                System.out.println(" ->  " + adj);
            }
        }
    }
}

输出：

orig: [4, 10]
 ->  [3, 9]
 ->  [3, 10]
 ->  [3, 11]
 ->  [4, 9]
 ->  [4, 11]
 ->  [5, 9]
 ->  [5, 10]
 ->  [5, 11]
orig: [100, 100]
 ->  [99, 99]
 ->  [99, 100]
 ->  [99, 101]
 ->  [100, 99]
 ->  [100, 101]
 ->  [101, 99]
 ->  [101, 100]
 ->  [101, 101]
orig: [1, 0]
 ->  [0, 0]
 ->  [0, 1]
 ->  [1, 1]
 ->  [2, 0]
 ->  [2, 1]

Answer 3

如果我理解正确，您需要列出给定location[x][y]的所有位置元素location[i][j]，其中(x,y)代表位置的{(i-1,j-1),(i+1,j+1),(i,j+1),(i+1,j),(i-1,j),(i,j-1),(i+1,j-1),(i-1,j+1)}索引集对属于该集合 reloadData

如何从另一个元素创建相邻元素的arraylist？

3 个答案: