为什么创建一个新对象 - Java Tetris 教程
我刚刚接触 Java，我发现了这个关于创建 Java 俄罗斯方块游戏的好教程。
我没有导师或导师来帮助我解决这个问题 - 我一直在寻找一位导师或导师:( 所以目前我正在自学 Java 和 PHP :)
无论如何，这是我找到的网站： http://zetcode.com /tutorials/javagamestutorial/tetris/
我在 Shape.java 类中没有得到的程序的一种方法：
public Shape rotateLeft()
{
if (pieceShape == Tetrominoes.SquareShape)
return this;
Shape result = new Shape();
result.pieceShape = pieceShape;
for (int i = 0; i < 4; ++i) {
result.setX(i, y(i));
result.setY(i, -x(i));
}
return result;
}
为什么我们需要创建一个新的对象 Shape result = new Shape (); 是否已经可以从 pieceShape 变量中获取当前块？
Im just new to Java and I found this good tutorial for creating a Java Tetris Game.
I dont have a mentor or a tutor to help me with this - Ive been looking for one for ages :(
so currently im self learning Java and PHP :)
Anyways heres the website I found: http://zetcode.com/tutorials/javagamestutorial/tetris/
One method of the program I dont get in the Shape.java class:
public Shape rotateLeft()
{
if (pieceShape == Tetrominoes.SquareShape)
return this;
Shape result = new Shape();
result.pieceShape = pieceShape;
for (int i = 0; i < 4; ++i) {
result.setX(i, y(i));
result.setY(i, -x(i));
}
return result;
}
Why do we need to create a new Object Shape result = new Shape(); if can already get the current piece from the pieceShape variable?
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评论（4）
本教程中的命名似乎有点误导。名为
Shape的类表示单个掉落的项目。Tetrominoesenum似乎描述了它是哪一种项目（即它的“形状”！）。因此，您发布的代码创建了一个新的项目并指定了其形状。
rotateRight()和rotateLeft()方法不会修改形状本身，以允许tryMove()方法检查移动是否正确合法，如果不合法则忽略它（例如，如果您将一个项目旋转到墙上）。当不允许移动时，tryMove()只是保留旧值（包括旧的Shape实例）。如果rotateLeft()/rotateRight()修改了Shape则必须撤消该操作，这会使代码变得复杂。此外，此代码还有一些挑剔之处：
我将
Tetrominoes类称为Tetromino，因为enum类型通常被命名为以单数形式（因为您经常引用单个元素：Tetromino.SquareShape。我将有关每个
Tetromino的具体坐标的信息添加到该enum中，有效地将setShape()方法中的大部分逻辑放入其中。Board 类混合了逻辑和表示，它应该分开（使其更容易测试）。
例如，
Board类可以实现所有逻辑，而无需任何图形（即不引用java.awt或javax.swing 中的任何内容） ）。然后，您将编写一个BoardPanel来绘制Board的状态并与用户交互，调用适当的Board方法。It seems the naming is a bit misleading in this tutorial. The class called
Shaperepresents a single item that falls down. TheTetrominoesenumseems to be describing which kind of item it is (i.e. it's "shape"!).So the code you posted creates a new item and specifies its shape.
The
rotateRight()androtateLeft()methods don't modify the shape itself to allow thetryMove()method to check if the move is legal and ignore it if it isn't (for example if you'd rotate an item into the wall).tryMove()simply keeps the old values (including the oldShapeinstance) when the move is not allowed. IfrotateLeft()/rotateRight()modified theShapethen it would have to undo that operation, which would complicate the code.Also, there are a few nitpicks with this code:
I'd call the
TetrominoesclassTetromino, asenumtypes are usually named in the singular (since you often reference a single element:Tetromino.SquareShape.I'd add the information about the concrete coordinate of each
Tetrominointo thatenum, effectively putting much of the logic from thesetShape()method into it.The
Boardclass mixes the logic and the presentation, it should be separated (makes it much easier to test).For example the
Boardclass could implement all the logic without any of the graphics (i.e. don't reference anything fromjava.awtorjavax.swing). Then you'd write aBoardPanelthat draws the state of theBoardand interacts with the user, calling the appropriateBoardmethods.您发布的方法返回一个向左旋转的形状。如果您没有创建新的形状，则原始形状（该类的一个字段并在其他地方使用）将被旋转。
对于正方形，向左旋转时不会改变，您仍然可以返回原始形状。
The method you've posted returns a shape that is rotated left. If you didn't create a new Shape, the original shape, which is a field of the class and used everywhere else, would have been rotated.
In the case of the square shape, which isn't changed when rotated left, you can still return the original one.
如果不仔细阅读教程，我会这样说：由于
Shape似乎代表一个单独的项目，并且rotateLeft()可能是Shape的实例方法code> 也可以就地旋转项目，即不返回旋转的副本，而是更改当前形状的块坐标。创建一个要掉落的新项目意味着创建一个具有默认方向的新Shape。Without looking thoroughly at the tutorial I'd say this: Since
Shapeseems to represent an individual item androtateLeft()might be a instance method ofShapeit might also be ok to rotate the item in place, i.e. not to return a rotated copy but change the block' coordinates of the current shape. Creating a new item to fall down would then mean to create a newShapewith default orientation.看来作者没有改变
rotateLeft()中的Shape，因为它可能不会被接受为有效的移动。在Board中，内部TAdapter类调用tryMove()并且仅设置当前Shape（变量curShape）如果可以接受的话。如果它在检查之前发生了变异，则必须在无效时将其设置回来。该方法或许应该命名为rotatedLeftCopy()，以表明它不会更改状态。或者应该事先执行检查，然后rotateLeft()就可以安全地更改Shape了。It appears that the author doesn't mutate the
ShapeinrotateLeft()because it might not be accepted as a valid move. InBoardthe innerTAdapterclass callstryMove()and only sets the currentShape(variablecurShape) if it's acceptable. If it were mutated prior to that check it'd have to set it back when invalid. The method should perhaps be namedrotatedLeftCopy()to indicate that it's not changing the state. Or the check should be performed beforehand and thenrotateLeft()would be safe to change theShapein place.