From 53e58ad41babd88b249a16e1566e6e8eceb26000 Mon Sep 17 00:00:00 2001
From: Gary Gregory <garydgregory@gmail.com>
Date: Fri, 12 Jul 2024 10:13:48 -0400
Subject: [PATCH] Javadoc

Use genaric parameter names that match the JRE
---
 .../commons/collections4/Transformer.java     |  4 +--
 .../comparators/TransformingComparator.java   |  4 +--
 .../functors/ChainedTransformer.java          |  1 +
 .../functors/CloneTransformer.java            |  1 +
 .../functors/ClosureTransformer.java          |  1 +
 .../functors/ConstantTransformer.java         | 12 ++++---
 .../functors/ExceptionTransformer.java        |  6 ++--
 .../functors/FactoryTransformer.java          | 12 ++++---
 .../collections4/functors/IfTransformer.java  | 27 ++++++++--------
 .../functors/InstantiateTransformer.java      |  1 +
 .../functors/InvokerTransformer.java          |  8 +++--
 .../collections4/functors/MapTransformer.java | 12 ++++---
 .../collections4/functors/NOPTransformer.java |  1 +
 .../functors/PredicateTransformer.java        |  1 +
 .../functors/StringValueTransformer.java      |  1 +
 .../functors/SwitchTransformer.java           | 32 ++++++++++---------
 .../iterators/TransformIterator.java          |  2 ++
 17 files changed, 73 insertions(+), 53 deletions(-)

diff --git a/src/main/java/org/apache/commons/collections4/Transformer.java b/src/main/java/org/apache/commons/collections4/Transformer.java
index 52bb97c10b..fada2391ee 100644
--- a/src/main/java/org/apache/commons/collections4/Transformer.java
+++ b/src/main/java/org/apache/commons/collections4/Transformer.java
@@ -33,8 +33,8 @@
  * cloning and returning the string value.
  * </p>
  *
- * @param <T> the input type to the transformer
- * @param <R> the output type from the transformer
+ * @param <T> the type of the input to the function.
+ * @param <R> the type of the result of the function.
  *
  * @since 1.0
  * @deprecated Use {@link Function}.
diff --git a/src/main/java/org/apache/commons/collections4/comparators/TransformingComparator.java b/src/main/java/org/apache/commons/collections4/comparators/TransformingComparator.java
index 74adfdb7e9..b8dbe4f0ec 100644
--- a/src/main/java/org/apache/commons/collections4/comparators/TransformingComparator.java
+++ b/src/main/java/org/apache/commons/collections4/comparators/TransformingComparator.java
@@ -31,8 +31,8 @@
  * This class is Serializable from Commons Collections 4.0.
  * </p>
  *
- * @param <I> the input type to the transformer
- * @param <O> the output type from the transformer
+ * @param <I> the type of the input to the function
+ * @param <O> the type of the result of the function
  *
  * @since 2.1
  *
diff --git a/src/main/java/org/apache/commons/collections4/functors/ChainedTransformer.java b/src/main/java/org/apache/commons/collections4/functors/ChainedTransformer.java
index 444f5bf919..b66da6a702 100644
--- a/src/main/java/org/apache/commons/collections4/functors/ChainedTransformer.java
+++ b/src/main/java/org/apache/commons/collections4/functors/ChainedTransformer.java
@@ -29,6 +29,7 @@
  * is passed to the second transformer and so on.
  * </p>
  *
+ * @param <T> the type of the input and result to the function.
  * @since 3.0
  */
 public class ChainedTransformer<T> implements Transformer<T, T>, Serializable {
diff --git a/src/main/java/org/apache/commons/collections4/functors/CloneTransformer.java b/src/main/java/org/apache/commons/collections4/functors/CloneTransformer.java
index ca1d3f28df..80eb586738 100644
--- a/src/main/java/org/apache/commons/collections4/functors/CloneTransformer.java
+++ b/src/main/java/org/apache/commons/collections4/functors/CloneTransformer.java
@@ -30,6 +30,7 @@
  * for more details.
  * </p>
  *
+ * @param <T> the type of the input and result to the function.
  * @since 3.0
  */
 public class CloneTransformer<T> implements Transformer<T, T> {
diff --git a/src/main/java/org/apache/commons/collections4/functors/ClosureTransformer.java b/src/main/java/org/apache/commons/collections4/functors/ClosureTransformer.java
index f329e5e871..411ab1fd16 100644
--- a/src/main/java/org/apache/commons/collections4/functors/ClosureTransformer.java
+++ b/src/main/java/org/apache/commons/collections4/functors/ClosureTransformer.java
@@ -26,6 +26,7 @@
  * Transformer implementation that calls a Closure using the input object
  * and then returns the input.
  *
+ * @param <T> the type of the input and result to the function.
  * @since 3.0
  */
 public class ClosureTransformer<T> implements Transformer<T, T>, Serializable {
diff --git a/src/main/java/org/apache/commons/collections4/functors/ConstantTransformer.java b/src/main/java/org/apache/commons/collections4/functors/ConstantTransformer.java
index 602ac38304..8db424086e 100644
--- a/src/main/java/org/apache/commons/collections4/functors/ConstantTransformer.java
+++ b/src/main/java/org/apache/commons/collections4/functors/ConstantTransformer.java
@@ -28,9 +28,11 @@
  * use the prototype factory.
  * </p>
  *
+ * @param <T> the type of the input to the function.
+ * @param <R> the type of the result of the function.
  * @since 3.0
  */
-public class ConstantTransformer<I, O> implements Transformer<I, O>, Serializable {
+public class ConstantTransformer<T, R> implements Transformer<T, R>, Serializable {
 
     /** Serial version UID */
     private static final long serialVersionUID = 6374440726369055124L;
@@ -66,7 +68,7 @@ public static <I, O> Transformer<I, O> nullTransformer() {
     }
 
     /** The closures to call in turn */
-    private final O iConstant;
+    private final R iConstant;
 
     /**
      * Constructor that performs no validation.
@@ -74,7 +76,7 @@ public static <I, O> Transformer<I, O> nullTransformer() {
      *
      * @param constantToReturn  the constant to return each time
      */
-    public ConstantTransformer(final O constantToReturn) {
+    public ConstantTransformer(final R constantToReturn) {
         iConstant = constantToReturn;
     }
 
@@ -99,7 +101,7 @@ public boolean equals(final Object obj) {
      * @return the constant
      * @since 3.1
      */
-    public O getConstant() {
+    public R getConstant() {
         return iConstant;
     }
 
@@ -122,7 +124,7 @@ public int hashCode() {
      * @return the stored constant
      */
     @Override
-    public O transform(final I input) {
+    public R transform(final T input) {
         return iConstant;
     }
 }
diff --git a/src/main/java/org/apache/commons/collections4/functors/ExceptionTransformer.java b/src/main/java/org/apache/commons/collections4/functors/ExceptionTransformer.java
index b5978605ee..52429a0da0 100644
--- a/src/main/java/org/apache/commons/collections4/functors/ExceptionTransformer.java
+++ b/src/main/java/org/apache/commons/collections4/functors/ExceptionTransformer.java
@@ -24,9 +24,11 @@
 /**
  * Transformer implementation that always throws an exception.
  *
+ * @param <T> the type of the input to the function.
+ * @param <R> the type of the result of the function.
  * @since 3.0
  */
-public final class ExceptionTransformer<I, O> implements Transformer<I, O>, Serializable {
+public final class ExceptionTransformer<T, R> implements Transformer<T, R>, Serializable {
 
     /** Serial version UID */
     private static final long serialVersionUID = 7179106032121985545L;
@@ -70,7 +72,7 @@ private Object readResolve() {
      * @throws FunctorException always
      */
     @Override
-    public O transform(final I input) {
+    public R transform(final T input) {
         throw new FunctorException("ExceptionTransformer invoked");
     }
 
diff --git a/src/main/java/org/apache/commons/collections4/functors/FactoryTransformer.java b/src/main/java/org/apache/commons/collections4/functors/FactoryTransformer.java
index 107bc96e1f..203c7e0906 100644
--- a/src/main/java/org/apache/commons/collections4/functors/FactoryTransformer.java
+++ b/src/main/java/org/apache/commons/collections4/functors/FactoryTransformer.java
@@ -25,9 +25,11 @@
 /**
  * Transformer implementation that calls a Factory and returns the result.
  *
+ * @param <T> the type of the input to the function.
+ * @param <R> the type of the result of the function.
  * @since 3.0
  */
-public class FactoryTransformer<I, O> implements Transformer<I, O>, Serializable {
+public class FactoryTransformer<T, R> implements Transformer<T, R>, Serializable {
 
     /** Serial version UID */
     private static final long serialVersionUID = -6817674502475353160L;
@@ -46,7 +48,7 @@ public static <I, O> Transformer<I, O> factoryTransformer(final Factory<? extend
     }
 
     /** The factory to wrap */
-    private final Factory<? extends O> iFactory;
+    private final Factory<? extends R> iFactory;
 
     /**
      * Constructor that performs no validation.
@@ -54,7 +56,7 @@ public static <I, O> Transformer<I, O> factoryTransformer(final Factory<? extend
      *
      * @param factory  the factory to call, not null
      */
-    public FactoryTransformer(final Factory<? extends O> factory) {
+    public FactoryTransformer(final Factory<? extends R> factory) {
         iFactory = factory;
     }
 
@@ -64,7 +66,7 @@ public FactoryTransformer(final Factory<? extends O> factory) {
      * @return the factory
      * @since 3.1
      */
-    public Factory<? extends O> getFactory() {
+    public Factory<? extends R> getFactory() {
         return iFactory;
     }
 
@@ -76,7 +78,7 @@ public Factory<? extends O> getFactory() {
      * @return the transformed result
      */
     @Override
-    public O transform(final I input) {
+    public R transform(final T input) {
         return iFactory.get();
     }
 
diff --git a/src/main/java/org/apache/commons/collections4/functors/IfTransformer.java b/src/main/java/org/apache/commons/collections4/functors/IfTransformer.java
index 787c43ae46..366753db3a 100644
--- a/src/main/java/org/apache/commons/collections4/functors/IfTransformer.java
+++ b/src/main/java/org/apache/commons/collections4/functors/IfTransformer.java
@@ -26,12 +26,11 @@
  * Transformer implementation that will call one of two closures based on whether a predicate evaluates
  * as true or false.
  *
- * @param <I> The input type for the transformer
- * @param <O> The output type for the transformer
- *
+ * @param <T> the type of the input to the function.
+ * @param <R> the type of the result of the function.
  * @since 4.1
  */
-public class IfTransformer<I, O> implements Transformer<I, O>, Serializable {
+public class IfTransformer<T, R> implements Transformer<T, R>, Serializable {
 
     /** Serial version UID */
     private static final long serialVersionUID = 8069309411242014252L;
@@ -73,13 +72,13 @@ public static <T> Transformer<T, T> ifTransformer(
                 Objects.requireNonNull(trueTransformer, "trueTransformer"), NOPTransformer.<T>nopTransformer());
     }
     /** The test */
-    private final Predicate<? super I> iPredicate;
+    private final Predicate<? super T> iPredicate;
 
     /** The transformer to use if true */
-    private final Transformer<? super I, ? extends O> iTrueTransformer;
+    private final Transformer<? super T, ? extends R> iTrueTransformer;
 
     /** The transformer to use if false */
-    private final Transformer<? super I, ? extends O> iFalseTransformer;
+    private final Transformer<? super T, ? extends R> iFalseTransformer;
 
     /**
      * Constructor that performs no validation.
@@ -89,9 +88,9 @@ public static <T> Transformer<T, T> ifTransformer(
      * @param trueTransformer  transformer used if true, not null
      * @param falseTransformer  transformer used if false, not null
      */
-    public IfTransformer(final Predicate<? super I> predicate,
-        final Transformer<? super I, ? extends O> trueTransformer,
-        final Transformer<? super I, ? extends O> falseTransformer) {
+    public IfTransformer(final Predicate<? super T> predicate,
+        final Transformer<? super T, ? extends R> trueTransformer,
+        final Transformer<? super T, ? extends R> falseTransformer) {
 
         iPredicate = predicate;
         iTrueTransformer = trueTransformer;
@@ -103,7 +102,7 @@ public IfTransformer(final Predicate<? super I> predicate,
      *
      * @return the transformer
      */
-    public Transformer<? super I, ? extends O> getFalseTransformer() {
+    public Transformer<? super T, ? extends R> getFalseTransformer() {
         return iFalseTransformer;
     }
 
@@ -112,7 +111,7 @@ public IfTransformer(final Predicate<? super I> predicate,
      *
      * @return the predicate
      */
-    public Predicate<? super I> getPredicate() {
+    public Predicate<? super T> getPredicate() {
         return iPredicate;
     }
 
@@ -121,7 +120,7 @@ public Predicate<? super I> getPredicate() {
      *
      * @return the transformer
      */
-    public Transformer<? super I, ? extends O> getTrueTransformer() {
+    public Transformer<? super T, ? extends R> getTrueTransformer() {
         return iTrueTransformer;
     }
 
@@ -132,7 +131,7 @@ public Predicate<? super I> getPredicate() {
      * @return the transformed result
      */
     @Override
-    public O transform(final I input) {
+    public R transform(final T input) {
         if (iPredicate.test(input)) {
             return iTrueTransformer.apply(input);
         }
diff --git a/src/main/java/org/apache/commons/collections4/functors/InstantiateTransformer.java b/src/main/java/org/apache/commons/collections4/functors/InstantiateTransformer.java
index a64c24b4e5..ed063feddb 100644
--- a/src/main/java/org/apache/commons/collections4/functors/InstantiateTransformer.java
+++ b/src/main/java/org/apache/commons/collections4/functors/InstantiateTransformer.java
@@ -31,6 +31,7 @@
  * for more details.
  * </p>
  *
+ * @param <T> the type of the input and result to the function.
  * @since 3.0
  */
 public class InstantiateTransformer<T> implements Transformer<Class<? extends T>, T> {
diff --git a/src/main/java/org/apache/commons/collections4/functors/InvokerTransformer.java b/src/main/java/org/apache/commons/collections4/functors/InvokerTransformer.java
index 5914bb30a7..353c6f8448 100644
--- a/src/main/java/org/apache/commons/collections4/functors/InvokerTransformer.java
+++ b/src/main/java/org/apache/commons/collections4/functors/InvokerTransformer.java
@@ -32,9 +32,11 @@
  * for more details.
  * </p>
  *
+ * @param <T> the type of the input to the function.
+ * @param <R> the type of the result of the function.
  * @since 3.0
  */
-public class InvokerTransformer<I, O> implements Transformer<I, O> {
+public class InvokerTransformer<T, R> implements Transformer<T, R> {
 
     /**
      * Gets an instance of this transformer calling a specific method with no arguments.
@@ -118,14 +120,14 @@ public InvokerTransformer(final String methodName, final Class<?>[] paramTypes,
      */
     @Override
     @SuppressWarnings("unchecked")
-    public O transform(final Object input) {
+    public R transform(final Object input) {
         if (input == null) {
             return null;
         }
         try {
             final Class<?> cls = input.getClass();
             final Method method = cls.getMethod(iMethodName, iParamTypes);
-            return (O) method.invoke(input, iArgs);
+            return (R) method.invoke(input, iArgs);
         } catch (final NoSuchMethodException ex) {
             throw new FunctorException("InvokerTransformer: The method '" + iMethodName + "' on '" +
                                        input.getClass() + "' does not exist");
diff --git a/src/main/java/org/apache/commons/collections4/functors/MapTransformer.java b/src/main/java/org/apache/commons/collections4/functors/MapTransformer.java
index d84cdec1a0..47e545e2dc 100644
--- a/src/main/java/org/apache/commons/collections4/functors/MapTransformer.java
+++ b/src/main/java/org/apache/commons/collections4/functors/MapTransformer.java
@@ -25,9 +25,11 @@
  * Transformer implementation that returns the value held in a specified map
  * using the input parameter as a key.
  *
+ * @param <T> the type of the input to the function.
+ * @param <R> the type of the result of the function.
  * @since 3.0
  */
-public final class MapTransformer<I, O> implements Transformer<I, O>, Serializable {
+public final class MapTransformer<T, R> implements Transformer<T, R>, Serializable {
 
     /** Serial version UID */
     private static final long serialVersionUID = 862391807045468939L;
@@ -50,7 +52,7 @@ public static <I, O> Transformer<I, O> mapTransformer(final Map<? super I, ? ext
     }
 
     /** The map of data to lookup in */
-    private final Map<? super I, ? extends O> iMap;
+    private final Map<? super T, ? extends R> iMap;
 
     /**
      * Constructor that performs no validation.
@@ -58,7 +60,7 @@ public static <I, O> Transformer<I, O> mapTransformer(final Map<? super I, ? ext
      *
      * @param map  the map to use for lookup, not cloned
      */
-    private MapTransformer(final Map<? super I, ? extends O> map) {
+    private MapTransformer(final Map<? super T, ? extends R> map) {
         iMap = map;
     }
 
@@ -68,7 +70,7 @@ private MapTransformer(final Map<? super I, ? extends O> map) {
      * @return the map
      * @since 3.1
      */
-    public Map<? super I, ? extends O> getMap() {
+    public Map<? super T, ? extends R> getMap() {
         return iMap;
     }
 
@@ -79,7 +81,7 @@ private MapTransformer(final Map<? super I, ? extends O> map) {
      * @return the transformed result
      */
     @Override
-    public O transform(final I input) {
+    public R transform(final T input) {
         return iMap.get(input);
     }
 
diff --git a/src/main/java/org/apache/commons/collections4/functors/NOPTransformer.java b/src/main/java/org/apache/commons/collections4/functors/NOPTransformer.java
index e025fc5531..29ab745225 100644
--- a/src/main/java/org/apache/commons/collections4/functors/NOPTransformer.java
+++ b/src/main/java/org/apache/commons/collections4/functors/NOPTransformer.java
@@ -23,6 +23,7 @@
 /**
  * Transformer implementation that does nothing.
  *
+ * @param <T> the type of the input and result to the function.
  * @since 3.0
  */
 public class NOPTransformer<T> implements Transformer<T, T>, Serializable {
diff --git a/src/main/java/org/apache/commons/collections4/functors/PredicateTransformer.java b/src/main/java/org/apache/commons/collections4/functors/PredicateTransformer.java
index 23319f976b..00fa8f0dc2 100644
--- a/src/main/java/org/apache/commons/collections4/functors/PredicateTransformer.java
+++ b/src/main/java/org/apache/commons/collections4/functors/PredicateTransformer.java
@@ -25,6 +25,7 @@
  * Transformer implementation that calls a Predicate using the input object
  * and then returns the result.
  *
+ * @param <T> the type of the input and result to the function.
  * @since 3.0
  */
 public class PredicateTransformer<T> implements Transformer<T, Boolean>, Serializable {
diff --git a/src/main/java/org/apache/commons/collections4/functors/StringValueTransformer.java b/src/main/java/org/apache/commons/collections4/functors/StringValueTransformer.java
index e39caa6cff..31c3fa3aa5 100644
--- a/src/main/java/org/apache/commons/collections4/functors/StringValueTransformer.java
+++ b/src/main/java/org/apache/commons/collections4/functors/StringValueTransformer.java
@@ -24,6 +24,7 @@
  * Transformer implementation that returns the result of calling
  * {@code String.valueOf} on the input object.
  *
+ * @param <T> the type of the input and result to the function.
  * @since 3.0
  */
 public final class StringValueTransformer<T> implements Transformer<T, String>, Serializable {
diff --git a/src/main/java/org/apache/commons/collections4/functors/SwitchTransformer.java b/src/main/java/org/apache/commons/collections4/functors/SwitchTransformer.java
index eb3dbfa959..4262bf0ed5 100644
--- a/src/main/java/org/apache/commons/collections4/functors/SwitchTransformer.java
+++ b/src/main/java/org/apache/commons/collections4/functors/SwitchTransformer.java
@@ -27,9 +27,11 @@
  * Transformer implementation calls the transformer whose predicate returns true,
  * like a switch statement.
  *
+ * @param <T> the type of the input to the function.
+ * @param <R> the type of the result of the function.
  * @since 3.0
  */
-public class SwitchTransformer<I, O> implements Transformer<I, O>, Serializable {
+public class SwitchTransformer<T, R> implements Transformer<T, R>, Serializable {
 
     /** Serial version UID */
     private static final long serialVersionUID = -6404460890903469332L;
@@ -108,13 +110,13 @@ public static <I, O> Transformer<I, O> switchTransformer(final Predicate<? super
         return new SwitchTransformer<>(predicates, transformers, defaultTransformer);
     }
     /** The tests to consider */
-    private final Predicate<? super I>[] iPredicates;
+    private final Predicate<? super T>[] iPredicates;
 
     /** The matching transformers to call */
-    private final Transformer<? super I, ? extends O>[] iTransformers;
+    private final Transformer<? super T, ? extends R>[] iTransformers;
 
     /** The default transformer to call if no tests match */
-    private final Transformer<? super I, ? extends O> iDefault;
+    private final Transformer<? super T, ? extends R> iDefault;
 
     /**
      * Hidden constructor for the use by the static factory methods.
@@ -124,13 +126,13 @@ public static <I, O> Transformer<I, O> switchTransformer(final Predicate<? super
      * @param transformers  matching array of transformers, no nulls
      * @param defaultTransformer  the transformer to use if no match, null means return null
      */
-    private SwitchTransformer(final boolean clone, final Predicate<? super I>[] predicates,
-                             final Transformer<? super I, ? extends O>[] transformers,
-                             final Transformer<? super I, ? extends O> defaultTransformer) {
+    private SwitchTransformer(final boolean clone, final Predicate<? super T>[] predicates,
+                             final Transformer<? super T, ? extends R>[] transformers,
+                             final Transformer<? super T, ? extends R> defaultTransformer) {
         iPredicates = clone ? FunctorUtils.copy(predicates) : predicates;
         iTransformers = clone ? FunctorUtils.copy(transformers) : transformers;
         iDefault = defaultTransformer == null ?
-                ConstantTransformer.<I, O>nullTransformer() : defaultTransformer;
+                ConstantTransformer.<T, R>nullTransformer() : defaultTransformer;
     }
 
     /**
@@ -141,9 +143,9 @@ private SwitchTransformer(final boolean clone, final Predicate<? super I>[] pred
      * @param transformers  matching array of transformers, cloned, no nulls
      * @param defaultTransformer  the transformer to use if no match, null means return null
      */
-    public SwitchTransformer(final Predicate<? super I>[] predicates,
-            final Transformer<? super I, ? extends O>[] transformers,
-            final Transformer<? super I, ? extends O> defaultTransformer) {
+    public SwitchTransformer(final Predicate<? super T>[] predicates,
+            final Transformer<? super T, ? extends R>[] transformers,
+            final Transformer<? super T, ? extends R> defaultTransformer) {
         this(true, predicates, transformers, defaultTransformer);
     }
 
@@ -153,7 +155,7 @@ public SwitchTransformer(final Predicate<? super I>[] predicates,
      * @return the default transformer
      * @since 3.1
      */
-    public Transformer<? super I, ? extends O> getDefaultTransformer() {
+    public Transformer<? super T, ? extends R> getDefaultTransformer() {
         return iDefault;
     }
 
@@ -163,7 +165,7 @@ public SwitchTransformer(final Predicate<? super I>[] predicates,
      * @return a copy of the predicates
      * @since 3.1
      */
-    public Predicate<? super I>[] getPredicates() {
+    public Predicate<? super T>[] getPredicates() {
         return FunctorUtils.copy(iPredicates);
     }
 
@@ -173,7 +175,7 @@ public Predicate<? super I>[] getPredicates() {
      * @return a copy of the transformers
      * @since 3.1
      */
-    public Transformer<? super I, ? extends O>[] getTransformers() {
+    public Transformer<? super T, ? extends R>[] getTransformers() {
         return FunctorUtils.copy(iTransformers);
     }
 
@@ -185,7 +187,7 @@ public Predicate<? super I>[] getPredicates() {
      * @return the transformed result
      */
     @Override
-    public O transform(final I input) {
+    public R transform(final T input) {
         for (int i = 0; i < iPredicates.length; i++) {
             if (iPredicates[i].test(input)) {
                 return iTransformers[i].apply(input);
diff --git a/src/main/java/org/apache/commons/collections4/iterators/TransformIterator.java b/src/main/java/org/apache/commons/collections4/iterators/TransformIterator.java
index 03f1a02099..1b3d774aca 100644
--- a/src/main/java/org/apache/commons/collections4/iterators/TransformIterator.java
+++ b/src/main/java/org/apache/commons/collections4/iterators/TransformIterator.java
@@ -23,6 +23,8 @@
 /**
  * Decorates an iterator such that each element returned is transformed.
  *
+ * @param <I> the type of the input to the function.
+ * @param <O> the type of the result of the function.
  * @since 1.0
  */
 public class TransformIterator<I, O> implements Iterator<O> {