2 files changed, 43 insertions, 12 deletions

diff --git a/src/main/java/org/zwobble/couscous/frontends/java/JavaFrontend.java b/src/main/java/org/zwobble/couscous/frontends/java/JavaFrontend.java
index d7bd54f..f58e6af 100644
--- a/src/main/java/org/zwobble/couscous/frontends/java/JavaFrontend.java
+++ b/src/main/java/org/zwobble/couscous/frontends/java/JavaFrontend.java
@@ -4,26 +4,21 @@ import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.List;
-import java.util.stream.Collectors;
 import java.util.stream.Stream;
+
 import org.zwobble.couscous.ast.ClassNode;
+import org.zwobble.couscous.util.ExtraLists;
 
 public class JavaFrontend {
     public static List<ClassNode> readSourceDirectory(Path directoryPath) throws IOException {
         JavaReader reader = new JavaReader();
-        return findJavaFiles(directoryPath)
-            .map(javaFile -> {
-                // TODO: unwrap exception in outer scope
-                try {
-                    return reader.readClassFromFile(directoryPath, javaFile);
-                } catch (Exception e) {
-                    throw new RuntimeException(e);
-                }                
-            })
-            .collect(Collectors.toList());
+        return ExtraLists.map(
+            findJavaFiles(directoryPath),
+            javaFile -> reader.readClassFromFile(directoryPath, javaFile));
     }
     
     private static Stream<Path> findJavaFiles(Path directoryPath) throws IOException {
-        return Files.walk(directoryPath).filter(path -> path.toFile().isFile() && path.toString().endsWith(".java"));
+        return Files.walk(directoryPath)
+            .filter(path -> path.toFile().isFile() && path.toString().endsWith(".java"));
     }
 }
\ No newline at end of file
diff --git a/src/main/java/org/zwobble/couscous/util/ExtraLists.java b/src/main/java/org/zwobble/couscous/util/ExtraLists.java
index b3c017f..36c9b06 100644
--- a/src/main/java/org/zwobble/couscous/util/ExtraLists.java
+++ b/src/main/java/org/zwobble/couscous/util/ExtraLists.java
@@ -3,8 +3,44 @@ package org.zwobble.couscous.util;
 import java.util.List;
 import java.util.function.BiFunction;
 import java.util.function.Function;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 public class ExtraLists {
+    @SuppressWarnings("unchecked")
+    public static <T, R, E extends Exception> List<R> map(
+            Stream<T> stream,
+            CheckedFunction<T, R, E> function) throws E {
+        try {
+            return stream
+                .map(value -> {
+                    try {
+                        return function.apply(value);
+                    } catch (Exception exception) {
+                        throw new StashedException(exception);
+                    }
+                })
+                .collect(Collectors.toList());
+        } catch (StashedException exception) {
+            throw (E)exception.exception;
+        }
+    }
+    
+    @FunctionalInterface
+    public static interface CheckedFunction<T, R, E extends Exception> {
+        R apply(T value) throws E;
+    }
+    
+    private static class StashedException extends RuntimeException {
+        private static final long serialVersionUID = 1L;
+        
+        private Exception exception;
+        
+        private StashedException(Exception exception) {
+            this.exception = exception;
+        }
+    }
+    
     public static <T, R> R foldLeft(
             List<T> list,
             Function<T, R> initialValue,