您如何使用java.util.regex.Pattern.Node

Question

I need to parse a sequence of Prolog statements and I've been putting together ad-hoc regexs to handle them but the result is not very robust. I noticed java.util.regex.Pattern.Prolog , which is a subclass of java.util.regex.Pattern.Node , but I can't seem to find anything that explains what these classes are for or how to use them. The Javadocs are mostly empty. Are there tutorials or fleshed-out documentation of the purpose and usage of these classes? Can they be used to parse Prolog?

Answer 1

Those classes have package access modifiers. For example, Node , in Oracle JDK 7, is declared as

static class Node extends Object {

They can only be accessed from classes in the same package. However, since that package is typically secured by the JVM, you cannot add your classes to it. You'll get an exception like

Exception in thread "main" java.lang.SecurityException: Prohibited package name: java.util.regex

You can find and copy the source code if you want, but you will not be able to use the classes themselves.

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As for their purpose, you have to again go to the source code and look at the comments.

/**
 * The following classes are the building components of the object
 * tree that represents a compiled regular expression. The object tree
 * is made of individual elements that handle constructs in the Pattern.
 * Each type of object knows how to match its equivalent construct with
 * the match() method.
 */