[英]Hiding methods of superclass
I've read the Overriding and Hiding Methods tutorial. 我已经阅读了Overriding and Hiding Methods教程。 And from that, I gathered the following:
从那以后,我收集了以下内容:
If a subclass defines a class method with the same signature as a class method in the superclass, the method in the subclass hides the one in the superclass.
如果子类定义的类方法与超类中的类方法具有相同的签名,则子类中的方法会隐藏超类中的方法。
As such, I did the following: 因此,我做了以下事情:
import javax.swing.JTextArea;
public final class JWrappedLabel extends JTextArea{
private static final long serialVersionUID = -844167470113830283L;
public JWrappedLabel(final String text){
super(text);
setOpaque(false);
setEditable(false);
setLineWrap(true);
setWrapStyleWord(true);
}
@Override
public void append(final String s){
throw new UnsupportedOperationException();
}
}
What I don't like about this design is that append
is still a visible method of the subclass. 我不喜欢这个设计的是
append
仍然是子类的可见方法。 Instead of throwing the UnsupportedOperationException
, I could have left the body empty. 我可以将身体留空,而不是抛出
UnsupportedOperationException
。 But both feel ugly. 但两人都觉得难看。
That being said, is there a better approach to hiding methods of the superclass? 话虽如此,有没有更好的方法来隐藏超类的方法?
Use composition, if possible. 如果可能,请使用合成。 This is recommended by Joshua Bloch in Effective Java, Second Edition .
这是Joshua Bloch在Effective Java,Second Edition中的推荐 。
Item 16: Favor composition over inheritance 第16项:赞成组合而不是继承
For example: 例如:
import javax.swing.JTextArea;
public final class JWrappedLabel {
private static final long serialVersionUID = -844167470113830283L;
private final JTextArea textArea;
public JWrappedLabel(final String text){
textArea = new JTextArea(text);
textArea.setOpaque(false);
textArea.setLineWrap(true);
textArea.setWrapStyleWord(true);
}
//add methods which delegate calls to the textArea
}
Nope that I know of. 不知道我知道的。
It is a OOP problem/feature. 这是一个OOP问题/功能。 You class still IS a JTextArea, and as such it could be used by code unaware of you subclass which would treat it as a JTextArea, expecting all of the method in JTextArea to be there and work properly.
你的类仍然是一个JTextArea,因此它可以被不知道你的子类的代码使用,它将它视为JTextArea,期望JTextArea中的所有方法都在那里并正常工作。
If you need to define a new interface, you should define a new class not extending JTextArea but instead encapsulating it. 如果需要定义新接口,则应定义一个不扩展JTextArea的新类,而是封装它。
是的,使用代理而不是扩展 。
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