NPE
2012-02-06 17:12:38
In the code, you're not creating an instance of the interface. Rather, the code defines an anonymous class that implements the interface, and instantiates that class.
The code is roughly equivalent to:
public final class Document {
private final class AnonymousContentVisitor implements ContentVisitor {
public void onStartDocument() {
throw new IllegalStateException();
}
public void onEndDocument() {
out.endDocument();
}
public void onEndTag() {
out.endTag();
inscopeNamespace.popContext();
activeNamespaces = null;
}
}
private final ContentVisitor visitor = new AnonymousContentVisitor();
}
thanks does this syntax(anonymous class) only saves us from writing some extra code or it has other advantages or uses too?
It saves having to write extra code and coming up with a name. The name is more likely to be
Document$1in the above example.@DesignCode: It's mainly syntactic sugar, but does have unique selling points as well. For example, if such a class is defined inside a function, it can access
finalvariables defined inside the function.