Java 优化技术（3）

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look_w发表于 2018-10-15 19:31 | 只看该作者

Java 优化技术（3）

Piece 类更有趣，因为我们需要一种方法来计算 Piece 的排列。我们可以通过先将块沿着其中一个单元的 6 条边旋转，上下翻转，最后再次沿着其中一个单元的 6 条边旋转。正如我们以前提到的，块由 5 个相邻的单元构成。翻转或旋转块就是翻转或旋转其所有单元。因此对于 Cell 对象，我们需要 flip() 和 rotate() 方法。通过相应地更改相邻的边就可以容易地实现翻转和旋转。在 Cell 类的 PieceCell 子类中提供了这些方法，如清单 3 所示。 PieceCell 对象是在 Piece 对象中使用的单元。
清单 3. PieceCell 子类

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public class PieceCell extends Cell {
  public void flip() {
Cell buffer = getNeighbour(NORTHEAST);
setNeighbour(NORTHEAST, getNeighbour(NORTHWEST));
setNeighbour(NORTHWEST, buffer);
buffer = getNeighbour(EAST);
setNeighbour(EAST, getNeighbour(WEST));
setNeighbour(WEST, buffer);
buffer = getNeighbour(SOUTHEAST);
setNeighbour(SOUTHEAST, getNeighbour(SOUTHWEST));
setNeighbour(SOUTHWEST, buffer);
  }
  public void rotate() {
// Clockwise rotation
Cell eastNeighbour = getNeighbour(EAST);
setNeighbour(EAST, getNeighbour(NORTHEAST));
setNeighbour(NORTHEAST, getNeighbour(NORTHWEST));
setNeighbour(NORTHWEST, getNeighbour(WEST));
setNeighbour(WEST, getNeighbour(SOUTHWEST));
setNeighbour(SOUTHWEST, getNeighbour(SOUTHEAST));
setNeighbour(SOUTHEAST, eastNeighbour);
  }
}

通过使用 PieceCell 类，我们可以完成 Piece 类的实现。清单 4 向您显示了源代码：
清单 4. Piece 类

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public class Piece {
  public static final int NUMBEROFCELLS = 5;
  public static final int NUMBEROFPERMUTATIONS = 12;
  private PieceCell[] pieceCells = new PieceCell[NUMBEROFCELLS];
  private int currentPermutation = 0;
  private void rotatePiece() {
for (int i = 0; i < NUMBEROFCELLS; i++) {
   pieceCells.rotate();
}
  }
  private void flipPiece() {
for (int i = 0; i < NUMBEROFCELLS; i++) {
   pieceCells.flip();
}
  }
  public Piece nextPermutation() {
if (currentPermutation == NUMBEROFPERMUTATIONS)
   currentPermutation = 0;
switch (currentPermutation%6) {
   case 0:
      // Flip after every 6 rotations
      flipPiece();
      break;
   default:
      rotatePiece();
      break;
}
currentPermutation++;
return this;
  }
  public void resetProcessed() {
for (int i = 0; i < NUMBEROFCELLS; i++) {
   pieceCells.setProcessed(false);
}
  }
  //Getters and setters have been omitted
}

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