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问题描述
初学者问题:如何将解析树的可读版本打印到标准输出?
Beginners question: how do I print a readable version of the parse tree to stdout?
CharStream input = CharStreams.fromFileName("testdata/test.txt");
MyLexer lexer = new MyLexer(input);
CommonTokenStream tokens = new CommonTokenStream(lexer);
MyParser parser = new MyParser(tokens);
parser.setBuildParseTree(true);
RuleContext tree = parser.record();
System.out.println(tree.toStringTree(parser));
这将在由括号()"分隔的一行上打印整个树.
this prints the whole tree on a single line delimited by brackets '()'.
(record (husband <4601> (name KOHAI Nikolaus) \n (birth * um.1872 (place Ploschitz)) \n\n) (wife (marriage oo) \n (name SCHLOTTHAUER Maria) \n (birth * um.1877
...
我想要这样的东西
record
husband
<id>
name
<name>
...
wife
推荐答案
摘自 SnippetsTest 作为独立实用程序类:
Extracted from SnippetsTest as a standalone utility class:
import java.util.List;
import org.antlr.v4.runtime.misc.Utils;
import org.antlr.v4.runtime.tree.Tree;
import org.antlr.v4.runtime.tree.Trees;
public class TreeUtils {
/** Platform dependent end-of-line marker */
public static final String Eol = System.lineSeparator();
/** The literal indent char(s) used for pretty-printing */
public static final String Indents = " ";
private static int level;
private TreeUtils() {}
/**
* Pretty print out a whole tree. {@link #getNodeText} is used on the node payloads to get the text
* for the nodes. (Derived from Trees.toStringTree(....))
*/
public static String toPrettyTree(final Tree t, final List<String> ruleNames) {
level = 0;
return process(t, ruleNames).replaceAll("(?m)^\\s+$", "").replaceAll("\\r?\\n\\r?\\n", Eol);
}
private static String process(final Tree t, final List<String> ruleNames) {
if (t.getChildCount() == 0) return Utils.escapeWhitespace(Trees.getNodeText(t, ruleNames), false);
StringBuilder sb = new StringBuilder();
sb.append(lead(level));
level++;
String s = Utils.escapeWhitespace(Trees.getNodeText(t, ruleNames), false);
sb.append(s + ' ');
for (int i = 0; i < t.getChildCount(); i++) {
sb.append(process(t.getChild(i), ruleNames));
}
level--;
sb.append(lead(level));
return sb.toString();
}
private static String lead(int level) {
StringBuilder sb = new StringBuilder();
if (level > 0) {
sb.append(Eol);
for (int cnt = 0; cnt < level; cnt++) {
sb.append(Indents);
}
}
return sb.toString();
}
}
调用方法如下:
List<String> ruleNamesList = Arrays.asList(parser.getRuleNames());
String prettyTree = TreeUtils.toPrettyTree(tree, ruleNamesList);
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