public final class DebugStringParser { private int lookahead = 0; private final int len; private final String source; public DebugStringParser(String s) { if(s == null || s.isEmpty()) throw new IllegalArgumentException("empty string!"); this.source = s; this.len = s.length(); } /** * Grammar: S -> ' '*
IF -> If (feature INT <= DOUBLE)
ELSE -> Else (feature INT > DOUBLE)
PREDICT -> Predict: DOUBLE
INT -> [+-]([1-9][0-9]+|0)
DOUBLE -> INT(\.[0-9]+)?([eE]INT)?
TREE -> IF\nTREE\nELSE\nTREE | PREDICT
* @return */ public Node parseAndGetRootNode(){ lookahead = 0; return mathTree(); } private Node mathTree(){ matchSpaces(); if(lookahead = len || source.charAt(lookahead++) != '\n') throw new IllegalArgumentException("line breaker is required."); } private ConditionEntry matchCondition(boolean isIfBranch){ if(isIfBranch) matchString("If (feature "); else matchString("Else (feature "); int mark = lookahead; matchInt(); int index = Integer.parseInt(source.substring(mark,lookahead)); if(isIfBranch) matchString(" <= "); else matchString(" > "); mark = lookahead; matchDouble(); double value = Double.parseDouble(source.substring(mark,lookahead)); if(lookahead >= len || source.charAt(lookahead++)!=')') throw new IllegalArgumentException("')' is required."); return new ConditionEntry(index,value); } private static final class ConditionEntry{ final int index; final double value; ConditionEntry(int index, double value) { this.index = index; this.value = value; } } private double matchPredict(){ matchString("Predict: "); int mark = lookahead; matchDouble(); return Double.parseDouble(source.substring(mark,lookahead)); } private void matchInt(){ char c; if(lookahead < len && ((c=source.charAt(lookahead)) == '+' || c == '-')) lookahead ++; if(lookahead = len || ((c=source.charAt(lookahead ++)) < '1') || c > '9') throw new IllegalArgumentException("[1-9] is expected."); while(lookahead < len && (c=source.charAt(lookahead)) >= '0' && c <='9') lookahead++; } private void matchDouble(){ char c; matchInt(); if(lookahead < len && source.charAt(lookahead) == '.'){ lookahead ++; while(lookahead < len && (c=source.charAt(lookahead)) >= '0' && c <='9') lookahead++; } if(lookahead = len || s.charAt(i) != source.charAt(lookahead++)) throw new IllegalArgumentException("expect '" + s + "' at " + (lookahead-i)); } } public static void main(String[] args) { String s = "If (feature 9 <= 0.0125)\n" + " If (feature 10 <= 0.0114)\n" + " If (feature 12 <= 0.0075)\n" + " If (feature 0 <= 0.0065)\n" + " If (feature 1 <= 0.0058)\n" + " Predict: 0.047923389851888445\n" + " Else (feature 1 > 0.0058)\n" + " Predict: 0.07137635126022983\n" + " Else (feature 0 > 0.0065)\n" + " If (feature 12 <= 0.0055)\n" + " Predict: 0.08800853325349002\n" + " Else (feature 12 > 0.0055)\n" + " Predict: 0.11735270545200469\n" + " Else (feature 12 > 0.0075)\n" + " If (feature 0 <= 0.0093)\n" + " If (feature 7 <= 0.0101)\n" + " Predict: 0.10974269542143679\n" + " Else (feature 7 > 0.0101)\n" + " Predict: 0.14264542094310068\n" + " Else (feature 0 > 0.0093)\n" + " If (feature 6 <= 0.0132)\n" + " Predict: 0.15816845060656223\n" + " Else (feature 6 > 0.0132)\n" + " Predict: 0.22484364604125084\n" + " Else (feature 10 > 0.0114)\n" + " If (feature 0 <= 0.0149)\n" + " If (feature 7 <= 0.011)\n" + " If (feature 2 <= 0.0199)\n" + " Predict: 0.17659115093907074\n" + " Else (feature 2 > 0.0199)\n" + " Predict: 0.11897248764689246\n" + " Else (feature 7 > 0.011)\n" + " If (feature 10 <= 0.0137)\n" + " Predict: 0.19971164036377678\n" + " Else (feature 10 > 0.0137)\n" + " Predict: 0.23499119198104446\n" + " Else (feature 0 > 0.0149)\n" + " If (feature 2 <= 0.0355)\n" + " If (feature 10 <= 0.0169)\n" + " Predict: 0.19316578816705413\n" + " Else (feature 10 > 0.0169)\n" + " Predict: 0.27050388273012166\n" + " Else (feature 2 > 0.0355)\n" + " If (feature 1 <= 0.0164)\n" + " Predict: 0.10299145299145299\n" + " Else (feature 1 > 0.0164)\n" + " Predict: 0.14485303437882907\n" + " Else (feature 9 > 0.0125)\n" + " If (feature 12 <= 0.0222)\n" + " If (feature 12 <= 0.0025)\n" + " If (feature 3 <= 0.0136)\n" + " If (feature 4 <= 0.0163)\n" + " Predict: 0.16205533596837945\n" + " Else (feature 4 > 0.0163)\n" + " Predict: 0.07920792079207921\n" + " Else (feature 3 > 0.0136)\n" + " If (feature 9 <= 0.2019)\n" + " Predict: 0.9225040850767459\n" + " Else (feature 9 > 0.2019)\n" + " Predict: 0.5019334880123744\n" + " Else (feature 12 > 0.0025)\n" + " If (feature 3 <= 0.0759)\n" + " If (feature 7 <= 0.0217)\n" + " Predict: 0.20286529220528218\n" + " Else (feature 7 > 0.0217)\n" + " Predict: 0.7116316639741519\n" + " Else (feature 3 > 0.0759)\n" + " If (feature 12 <= 0.0082)\n" + " Predict: 0.1456244234832029\n" + " Else (feature 12 > 0.0082)\n" + " Predict: 0.6139024177696873\n" + " Else (feature 12 > 0.0222)\n" + " If (feature 3 <= 0.0136)\n" + " If (feature 0 <= 0.0149)\n" + " If (feature 14 <= 0.0089)\n" + " Predict: 0.11330472103004292\n" + " Else (feature 14 > 0.0089)\n" + " Predict: 0.16452830188679246\n" + " Else (feature 0 > 0.0149)\n" + " If (feature 11 <= 0.0167)\n" + " Predict: 0.17938517179023508\n" + " Else (feature 11 > 0.0167)\n" + " Predict: 0.27445605619325\n" + " Else (feature 3 > 0.0136)\n" + " If (feature 2 <= 0.0355)\n" + " If (feature 4 <= 0.0186)\n" + " Predict: 0.7787088347055098\n" + " Else (feature 4 > 0.0186)\n" + " Predict: 0.9376800209478922\n" + " Else (feature 2 > 0.0355)\n" + " If (feature 3 <= 0.0759)\n" + " Predict: 0.9172398148052672\n" + " Else (feature 3 > 0.0759)\n" + " Predict: 0.985060246603449"; DebugStringParser parser = new DebugStringParser(s); System.out.println(parser.parseAndGetRootNode()); }}public final class Node implements Serializable { private static final long serialVersionUID = 273479971015393598L; private final Node left; private final Node right; private final boolean leaf; private final int featureIndex; private final double featureValue; Node(Node left, Node right, boolean leaf, int featureIndex, double featureValue) { if((!leaf) ? (left == null && right ==null):(left != null && right != null)) throw new IllegalArgumentException("illegal leaf:"+ leaf); this.left = left; this.right = right; this.leaf = leaf; this.featureIndex = featureIndex; this.featureValue = featureValue; } public Node getLeft() { return left; } public Node getRight() { return right; } public boolean isLeaf() { return leaf; } public int getFeatureIndex() { return featureIndex; } public double getFeatureValue() { return featureValue; } @Override public String toString() { StringBuilder builder = new StringBuilder(); toString(builder,""); return builder.toString(); } private void toString(StringBuilder builder,String prefix){ if(isLeaf()){ builder.append(prefix) .append("Predict: ") .append(featureValue); return; } builder.append(prefix) .append("If (feature ") .append(featureIndex) .append(" <= ") .append(featureValue) .append(")\n"); String tab = " " + prefix; left.toString(builder, tab); builder .append('\n') .append(prefix) .append("Else (feature ") .append(featureIndex) .append(" > ") .append(featureValue) .append(")\n"); right.toString(builder, tab); }}