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Original file line number	Diff line number	Diff line change
`@@ -202,7 +202,7 @@ void doSomething(Shape shape) {`
`202`	`202`	```java
`203`	`203`	`doSomething(circle);`
`204`	`204`	```
`205`		`-当预期接收 Shape 的方法被传入了 Circle，会发生什么。由于 Circle 也是一种 Shape，所`
	`205`	`+当预期接收 Shape 的方法被传入了 Circle，会发生什么。由于 Circle 也是一种 Shape，所`
`206`	`206`	以 `doSomething(circle)` 能正确地执行。也就是说，`doSomething()` 能接收任意发送给 Shape 的消息。这是完全安全和合乎逻辑的事情。
`207`	`207`
`208`	`208`	这种把子类当成其基类来处理的过程叫做“向上转型”（upcasting）。在面向对象的编程里，经常利用这种方法来给程序解耦。再看下面的 `doSomething()` 代码示例：

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