Question

如何在validCell中修改传入validCell的“list”，然后返回修改后的列表？ validCell接受参数并检查是否可以从r＆amp; amp;给出的起始点找到拼写出“单词”的单元格的路径。 cellForWord中的for循环的c。我认为我所拥有的是正确的。

public class GoodWordOnBoardFinder implements IWordOnBoardFinder {

@Override
public List<BoardCell> cellsForWord(BoggleBoard board, String word) {
    // TODO Auto-generated method stub
    List<BoardCell> list = new ArrayList<BoardCell>();
    //Loop through each cell on board to find a starting point
       for(int r=0; r < board.size(); r++)
       {
           for(int c=0; c < board.size(); c++)
           {
              if(validCell(board, r, c, list, word, 0))
                  return list;
                   //***HOW to get populated list NOT Blank list???
           }
       }
    return null;
}
public boolean validCell(BoggleBoard theBoard, int row, int col, List<BoardCell> cList, String theWord, int letterIndex ){

    BoardCell cell = new BoardCell(row, col);

   String letter = theWord.substring(letterIndex, letterIndex+1);
    //Check the whole world has been found
   if(letterIndex >= theWord.length())
       return true;

   //Check if row or column is off the board
   if(row > theBoard.size() || col > theBoard.size())
       return false;
   //Check if cell has already been visited
   if(cList.contains(cell))
       return false;
   //Check if cell face isn't the letter we're looking for
   if(!theBoard.getFace(row, col).equals(letter))
   {
       //Make sure the letter isn't a Q bc Boggle is special
       if(!(theBoard.getFace(row, col).equals("Qu") && letter.equals("q")))
           return true;
   }
   cList.add(cell); 

  //Check all neighboring cells for letters of the word
  int[] rdelta = {-1,-1,-1, 0, 0, 1, 1, 1};
  int[] cdelta = {-1, 0, 1,-1, 1,-1, 0, 1};
  for(int k=0; k < rdelta.length; k++){
    if (validCell(theBoard, row+rdelta[k], col+cdelta[k], cList, theWord, letterIndex+1))
        return true;
   }
  cList.remove(cell);
return false;
}

}

Answer 1

在Java中，对象按值传递（参见this response）。这实质上意味着传入对象本身的引用，并将其转换回原始对象，而不是对象的副本。你可以修改列表而不用担心返回它，因为任何修改都会保留。

Example:
List<String> test = new ArrayList<String>();
test.add("Test 1");
OtherClass otherClass = new OtherClass(test);
...
otherClass.modifyList(test);
...
System.out.println(test.size());

在此示例中，modifyList将假设将另一个字符串添加到传入列表中。

Answer 2

您在validCell中所做的任何更改cList都会自动反映到原始列表中。

Java是按值传递的：在这种情况下，它传递引用的值。所以两者都将指向同一个对象。在validCell中对cList所做的任何更改都将反映在list上。

Answer 3

考虑将列表转换为类成员。那么你不必将它传递给方法：

public class GoodWordOnBoardFinder implements IWordOnBoardFinder {

   // The board
   List<BoardCell> board;

   // methods
   public boolean validCell(BoggleBoard theBoard, int row, int col, String theWord, int letterIndex ){
     // access/modify the board (= what you called cList)
   }
}

如何在方法之间修改List？

3 个答案: