java - 如何修改方法之间的列表？

Question

如何在validCell中修改传递给validCell的“列表”，然后返回修改后的列表？validCell 获取参数并检查是否可以从 cellsForWord 中 for 循环的 r & c 给出的起点找到拼写“单词”的单元格路径。我不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;
}

}

score 0 · Accepted Answer

In Java, Objects are passed byval (see this response). This essentially means that a reference to the object itself is passed in, and translated back into the original object, not a copy of the object. You can just modify list and not worry about returning it, as any modifications will be kept.

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

In this example, modifyList will hypothetically add another string to the passed in list.

score 0 · Accepted Answer

Any changes you make cList inside the validCell will automatically be reflected to the original list.

Java is pass by value: In this case it is passing the value of the reference. So both will be pointing to the same object. Any changes made in validCell to cList will reflect on list.

score 0 · Accepted Answer

考虑将列表转换为类成员。然后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)
   }
}

java - 如何修改方法之间的列表？

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