we are moving form post dominators.

src/CFGBuilder.java

@@ -0,0 +1,130 @@
+import org.lsmr.cfg.*;
+import org.antlr.v4.runtime.*;
+import org.antlr.v4.runtime.tree.*;
+import java.io.*;
+import java.util.*;
+
+public class CFGBuilder {
+
+    private Map<Node, Integer> nodeToLine = new HashMap<>();
+
+    /**
+     * Build CFG from a Java file
+     */
+    public ControlFlowGraph buildFromFile(String filename) throws IOException {
+        System.out.println("\n\tBuilding CFG from " + filename);
+
+        // Parse the file
+        CharStream input = CharStreams.fromFileName(filename);
+        Java1_4Lexer lexer = new Java1_4Lexer(input);
+        CommonTokenStream tokens = new CommonTokenStream(lexer);
+        Java1_4Parser parser = new Java1_4Parser(tokens);
+
+        parser.removeErrorListeners();
+
+        ParseTree tree = parser.compilationUnit();
+
+        // build CFG using professor's NodeBuilder
+        NodeBuilder builder = new NodeBuilder();
+        builder.visit(tree);
+
+        List<ControlFlowGraph> cfgs = builder.getCFGs();
+
+        if (cfgs.isEmpty()) {
+            throw new RuntimeException("No methods found in file");
+        }
+
+        if (cfgs.size() > 1) {
+            System.out.println("Note: File has " + cfgs.size() + " methods, using first method");
+        }
+
+        ControlFlowGraph cfg = cfgs.get(0);
+
+        extractLineNumbers(cfg, tree);
+
+        System.out.println("CFG built: " + cfg.nodes().size() + " nodes, " + cfg.edges().size() + " edges");
+
+        return cfg;
+    }
+    private void extractLineNumbers(ControlFlowGraph cfg, ParseTree tree) {
+        Map<String, Integer> labelToLine = new HashMap<>();
+        collectLineNumbers(tree, labelToLine);
+
+        for (Node node : cfg.nodes()) {
+            String label = node.label();
+            Integer line = labelToLine.get(label);
+
+            if (line == null) {
+                for (Map.Entry<String, Integer> entry : labelToLine.entrySet()) {
+                    if (label.contains(entry.getKey()) || entry.getKey().contains(label)) {
+                        line = entry.getValue();
+                        break;
+                    }
+                }
+            }
+
+            nodeToLine.put(node, line != null ? line : -1);
+        }
+    }
+
+
+    private void collectLineNumbers(ParseTree tree, Map<String, Integer> map) {
+        if (tree instanceof ParserRuleContext) {
+            ParserRuleContext ctx = (ParserRuleContext) tree;
+            if (ctx.start != null) {
+                String text = ctx.getText();
+                if (text != null && text.length() < 200 && text.length() > 0) {
+                    map.put(text, ctx.start.getLine());
+                }
+            }
+        }
+
+        for (int i = 0; i < tree.getChildCount(); i++) {
+            collectLineNumbers(tree.getChild(i), map);
+        }
+    }
+
+
+    public int getLineNumber(Node node) {
+        return nodeToLine.getOrDefault(node, -1);
+    }
+
+    public List<Integer> getAllLineNumbers() {
+        Set<Integer> lines = new TreeSet<>();
+        for (Integer line : nodeToLine.values()) {
+            if (line > 0) lines.add(line);
+        }
+        return new ArrayList<>(lines);
+    }
+
+    public List<Node> findNodesAtLine(ControlFlowGraph cfg, int lineNumber) {
+        List<Node> result = new ArrayList<>();
+        for (Node node : cfg.nodes()) {
+            if (getLineNumber(node) == lineNumber) {
+                result.add(node);
+            }
+        }
+        return result;
+    }
+
+    public void printLineMapping(ControlFlowGraph cfg) {
+        System.out.println("\n Line Number Mapping");
+        Map<Integer, List<String>> lineToNodes = new TreeMap<>();
+
+        for (Node node : cfg.nodes()) {
+            int line = getLineNumber(node);
+            if (line > 0) {
+                lineToNodes.putIfAbsent(line, new ArrayList<>());
+                lineToNodes.get(line).add(node.label());
+            }
+        }
+
+        for (Map.Entry<Integer, List<String>> entry : lineToNodes.entrySet()) {
+            System.out.println("Line " + entry.getKey() + ":");
+            for (String label : entry.getValue()) {
+                System.out.println("  " + label);
+            }
+        }
+        System.out.println();
+    }
+}