将非泛型类扩展为通用类
[英] Extending a non-generic class to a generic class
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问题描述
包org.apache.commons.collections.buffer中的Java类CircularFifoBuffer是非通用的，可以存储任何类的对象。
创建一个只有T类对象的泛型版本。我的第一个想法是扩展CircularFifoBuffer并简单地写一个新的'add'方法：
public class CircularFifoQueue< T> extends CircularFifoBuffer {
public boolean add（T data）{
return super.add（data）;
}
}
add'方法，允许添加任意类的对象。有没有办法使用继承而不是组合（所以我不必重新实现所有的CircularFifoBuffer的方法），但阻止类的用户添加非T对象？
public class CircularFifoQueue< T> {
private CircularFifoBuffer buffer = new CircularFifoBuffer（）;
public boolean add（T data）{
return buffer.add（data）;
}
//实现所需的所有其他方法
}
b $ b
所以内部缓冲区接受一切，但是包装器确保只能添加 T 类型对象。问题：现在缓冲区没有实现任何接口。所以它的用法现在有点有限（如果你需要发送一个 Buffer 例如不能使用它）
The Java class CircularFifoBuffer in the package org.apache.commons.collections.buffer is non-generic, and can store objects of any class.
I would like to create a generified version of this, that can only hold objects of class T. My first thought was to extend CircularFifoBuffer and simply write a new 'add' method:
public class CircularFifoQueue<T> extends CircularFifoBuffer {
public boolean add(T data) {
return super.add(data);
}
}
However, this leaves the old 'add' method in place, allowing for objects of arbitrary class to be added. Is there a way around this that uses inheritance rather than composition (so that I don't have to re-implement all of CircularFifoBuffer's methods) but prevents users of the class from adding non-T objects?
解决方案
One idea is t implement your own buffer that just wraps the original one:
public class CircularFifoQueue<T> {
private CircularFifoBuffer buffer = new CircularFifoBuffer();
public boolean add(T data) {
return buffer.add(data);
}
// implement all other methods that are needed
}
So the internal buffer takes everything but the wrapper makes sure that only T type objects can be added. Problem: right now the buffer does not implement any interface. So it's usage is a bit limited right now (you can't use it if you need to send a Buffer for example)
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