diff --git a/tools/adventure-pack/goodies/java/build.gradle.kts b/tools/adventure-pack/goodies/java/build.gradle.kts
index b40b09db..a34cf238 100644
--- a/tools/adventure-pack/goodies/java/build.gradle.kts
+++ b/tools/adventure-pack/goodies/java/build.gradle.kts
@@ -48,3 +48,9 @@ tasks.register<KtfmtFormatTask>("ktfmtCustom") {
   source = project.fileTree(rootDir)
   include("*.gradle.kts")
 }
+
+tasks.withType<JavaCompile> {
+  options.compilerArgs.add("-Xlint:all")
+  options.compilerArgs.add("-Werror")
+  options.isWarnings = true
+}
diff --git a/tools/adventure-pack/goodies/java/src/simple_iterator/SimpleIterator.java b/tools/adventure-pack/goodies/java/src/simple_iterator/SimpleIterator.java
new file mode 100644
index 00000000..67ea9eaa
--- /dev/null
+++ b/tools/adventure-pack/goodies/java/src/simple_iterator/SimpleIterator.java
@@ -0,0 +1,52 @@
+package simple_iterator;
+
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+
+public interface SimpleIterator<T> {
+  public T next();
+
+  static enum HasNextState {
+    TRUE,
+    FALSE,
+    UNKNOWN,
+  }
+
+  public static <T> Iterator<T> toIterator(final SimpleIterator<T> iterator) {
+    final HasNextState[] hasNextState = { HasNextState.UNKNOWN };
+    final Object[] elementReserve = { null };
+
+    return new Iterator<T>() {
+      public boolean hasNext() {
+        if (hasNextState[0] == HasNextState.UNKNOWN) {
+          try {
+            elementReserve[0] = iterator.next();
+            hasNextState[0] = HasNextState.TRUE;
+          } catch (NoSuchElementException e) {
+            hasNextState[0] = HasNextState.FALSE;
+          }
+        }
+
+        return hasNextState[0] == HasNextState.TRUE;
+      }
+
+      public T next() {
+        if (hasNextState[0] == HasNextState.TRUE) {
+          hasNextState[0] = HasNextState.UNKNOWN;
+
+          @SuppressWarnings("unchecked")
+          T element = (T) elementReserve[0];
+
+          elementReserve[0] = null;
+          return element;
+        }
+
+        if (hasNextState[0] == HasNextState.UNKNOWN) {
+          return iterator.next();
+        }
+
+        throw new NoSuchElementException();
+      }
+    };
+  }
+}
diff --git a/tools/adventure-pack/goodies/java/src/simple_iterator/goody.json b/tools/adventure-pack/goodies/java/src/simple_iterator/goody.json
new file mode 100644
index 00000000..a38d0e52
--- /dev/null
+++ b/tools/adventure-pack/goodies/java/src/simple_iterator/goody.json
@@ -0,0 +1,3 @@
+{
+  "name": "SimpleIterator"
+}
diff --git a/tools/adventure-pack/goodies/java/src/to_iterable/AP.java b/tools/adventure-pack/goodies/java/src/to_iterable/AP.java
index f6247dd6..b064f8fc 100644
--- a/tools/adventure-pack/goodies/java/src/to_iterable/AP.java
+++ b/tools/adventure-pack/goodies/java/src/to_iterable/AP.java
@@ -2,7 +2,7 @@
 
 final class AP {
 
-  public static <T> Iterable<T> toIterable(Iterator<T> iterator) {
+  public static <T> Iterable<T> toIterable(final Iterator<T> iterator) {
     return () -> iterator;
   }
 }
diff --git a/tools/adventure-pack/goodies/kotlin/build.gradle.kts b/tools/adventure-pack/goodies/kotlin/build.gradle.kts
index 302bd29d..c51c4fea 100644
--- a/tools/adventure-pack/goodies/kotlin/build.gradle.kts
+++ b/tools/adventure-pack/goodies/kotlin/build.gradle.kts
@@ -44,3 +44,5 @@ tasks.register<KtfmtFormatTask>("ktfmtCustom") {
   include("*.gradle.kts")
   include("**/*.kt")
 }
+
+// TODO: Kotlin equivalent of -Xlint:all
diff --git a/tools/adventure-pack/src/app/__tests__/__snapshots__/equip-test.ts.snap b/tools/adventure-pack/src/app/__tests__/__snapshots__/equip-test.ts.snap
index 335b500c..0eaf4c5b 100644
--- a/tools/adventure-pack/src/app/__tests__/__snapshots__/equip-test.ts.snap
+++ b/tools/adventure-pack/src/app/__tests__/__snapshots__/equip-test.ts.snap
@@ -10,6 +10,65 @@ record Pair<TFirst, TSecond>(TFirst first, TSecond second) {}
 /////////////////////////// END ADVENTURE PACK CODE ////////////////////////////"
 `;
 
+exports[`App can equip single goody: Java SimpleIterator 1`] = `
+"////////////////////////// BEGIN ADVENTURE PACK CODE ///////////////////////////
+// Adventure Pack commit fake-commit-hash
+// Running at: https://example.com/
+
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+
+interface SimpleIterator<T> {
+  public T next();
+
+  static enum HasNextState {
+    TRUE,
+    FALSE,
+    UNKNOWN,
+  }
+
+  public static <T> Iterator<T> toIterator(final SimpleIterator<T> iterator) {
+    final HasNextState[] hasNextState = { HasNextState.UNKNOWN };
+    final Object[] elementReserve = { null };
+
+    return new Iterator<T>() {
+      public boolean hasNext() {
+        if (hasNextState[0] == HasNextState.UNKNOWN) {
+          try {
+            elementReserve[0] = iterator.next();
+            hasNextState[0] = HasNextState.TRUE;
+          } catch (NoSuchElementException e) {
+            hasNextState[0] = HasNextState.FALSE;
+          }
+        }
+
+        return hasNextState[0] == HasNextState.TRUE;
+      }
+
+      public T next() {
+        if (hasNextState[0] == HasNextState.TRUE) {
+          hasNextState[0] = HasNextState.UNKNOWN;
+
+          @SuppressWarnings("unchecked")
+          T element = (T) elementReserve[0];
+
+          elementReserve[0] = null;
+          return element;
+        }
+
+        if (hasNextState[0] == HasNextState.UNKNOWN) {
+          return iterator.next();
+        }
+
+        throw new NoSuchElementException();
+      }
+    };
+  }
+}
+
+/////////////////////////// END ADVENTURE PACK CODE ////////////////////////////"
+`;
+
 exports[`App can equip single goody: Java UnionFind 1`] = `
 "////////////////////////// BEGIN ADVENTURE PACK CODE ///////////////////////////
 // Adventure Pack commit fake-commit-hash
@@ -118,7 +177,7 @@ import java.util.Iterator;
 final class AP {
   private AP() {}
 
-  public static <T> Iterable<T> toIterable(Iterator<T> iterator) {
+  public static <T> Iterable<T> toIterable(final Iterator<T> iterator) {
     return () -> iterator;
   }
 }
diff --git a/tools/adventure-pack/src/app/__tests__/__snapshots__/render-test.ts.snap b/tools/adventure-pack/src/app/__tests__/__snapshots__/render-test.ts.snap
index d1b992f4..23cc7084 100644
--- a/tools/adventure-pack/src/app/__tests__/__snapshots__/render-test.ts.snap
+++ b/tools/adventure-pack/src/app/__tests__/__snapshots__/render-test.ts.snap
@@ -6,6 +6,61 @@ exports[`App can render goody: Java Pair 1`] = `
 record Pair<TFirst, TSecond>(TFirst first, TSecond second) {}"
 `;
 
+exports[`App can render goody: Java SimpleIterator 1`] = `
+"package simple_iterator;
+
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+
+interface SimpleIterator<T> {
+  public T next();
+
+  static enum HasNextState {
+    TRUE,
+    FALSE,
+    UNKNOWN,
+  }
+
+  public static <T> Iterator<T> toIterator(final SimpleIterator<T> iterator) {
+    final HasNextState[] hasNextState = { HasNextState.UNKNOWN };
+    final Object[] elementReserve = { null };
+
+    return new Iterator<T>() {
+      public boolean hasNext() {
+        if (hasNextState[0] == HasNextState.UNKNOWN) {
+          try {
+            elementReserve[0] = iterator.next();
+            hasNextState[0] = HasNextState.TRUE;
+          } catch (NoSuchElementException e) {
+            hasNextState[0] = HasNextState.FALSE;
+          }
+        }
+
+        return hasNextState[0] == HasNextState.TRUE;
+      }
+
+      public T next() {
+        if (hasNextState[0] == HasNextState.TRUE) {
+          hasNextState[0] = HasNextState.UNKNOWN;
+
+          @SuppressWarnings("unchecked")
+          T element = (T) elementReserve[0];
+
+          elementReserve[0] = null;
+          return element;
+        }
+
+        if (hasNextState[0] == HasNextState.UNKNOWN) {
+          return iterator.next();
+        }
+
+        throw new NoSuchElementException();
+      }
+    };
+  }
+}"
+`;
+
 exports[`App can render goody: Java UnionFind 1`] = `
 "package union_find;
 
@@ -86,7 +141,7 @@ import java.util.Iterator;
 final class AP {
   private AP() {}
 
-  public static <T> Iterable<T> toIterable(Iterator<T> iterator) {
+  public static <T> Iterable<T> toIterable(final Iterator<T> iterator) {
     return () -> iterator;
   }
 }"