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[java] keyword 'final'

2009-05-24 05:46:06| 分类： lang_java | 标签： |举报 |字号大中小订阅

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对于变量，final 就是 C++ 中 const 的意思。
final int a = 10;
a = 20;   // not allow

而 final 作为类/函数的修饰符时，则表示是否能 override。
final class Foo {}
class Bar extends Foo {} // not allow

class Foo {
    public final void baby() {}
}
class Bar extends Foo {
    public void baby() {}   // not allow
}
对于类，有了 final 后，就不能被继承了，这是一种编译器强制行为。而 C++ 通过是否有 virtual dtor 语义上决定一个类是否允许继承，则多少有点隐晦。
java 中所有 class method 默认都是 virtual function，使用 final 修饰后，此函数不能被 override。C++中默认函数都是 non-virtual function，也允许子类 override。

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