在我的 AP 计算机科学课上，我们一直在学习GridWorld案例研究。看着它，似乎 AbstractGrid 类没有抽象的理由，因为它没有抽象方法或值。为什么会这样？
更多信息
如果只是强制实现 Grid 接口，为什么不将这些方法作为抽象方法（因此在没有接口的情况下强制这些类的签名）。此外，无论如何，这两个孩子都会覆盖它的大部分方法。
package info.gridworld.grid;
import java.util.ArrayList;
public abstract class AbstractGrid<E> implements Grid<E>
{
public ArrayList<E> getNeighbors(Location loc)
{
ArrayList<E> neighbors = new ArrayList<E>();
for (Location neighborLoc : getOccupiedAdjacentLocations(loc))
neighbors.add(get(neighborLoc));
return neighbors;
}
public ArrayList<Location> getValidAdjacentLocations(Location loc)
{
ArrayList<Location> locs = new ArrayList<Location>();
int d = Location.NORTH;
for (int i = 0; i < Location.FULL_CIRCLE / Location.HALF_RIGHT; i++)
{
Location neighborLoc = loc.getAdjacentLocation(d);
if (isValid(neighborLoc))
locs.add(neighborLoc);
d = d + Location.HALF_RIGHT;
}
return locs;
}
public ArrayList<Location> getEmptyAdjacentLocations(Location loc)
{
ArrayList<Location> locs = new ArrayList<Location>();
for (Location neighborLoc : getValidAdjacentLocations(loc))
{
if (get(neighborLoc) == null)
locs.add(neighborLoc);
}
return locs;
}
public ArrayList<Location> getOccupiedAdjacentLocations(Location loc)
{
ArrayList<Location> locs = new ArrayList<Location>();
for (Location neighborLoc : getValidAdjacentLocations(loc))
{
if (get(neighborLoc) != null)
locs.add(neighborLoc);
}
return locs;
}
/**
* Creates a string that describes this grid.
* @return a string with descriptions of all objects in this grid (not
* necessarily in any particular order), in the format {loc=obj, loc=obj,
* ...}
*/
public String toString()
{
String s = "{";
for (Location loc : getOccupiedLocations())
{
if (s.length() > 1)
s += ", ";
s += loc + "=" + get(loc);
}
return s + "}";
}
}