Internally work with 'ImmutableList' instead of plain 'List'

Author: ribeach1

src/main/java/org/apache/camel/component/dataprovider/LazyDataProvider.java

@@ -1,8 +1,8 @@
 package org.apache.camel.component.dataprovider;
 
+import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Range;
 
-import java.util.List;
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantReadWriteLock;
 
@@ -21,19 +21,27 @@ public abstract class LazyDataProvider<T> implements IDataProvider<T> {
     private final Lock readDataLock = dataLock.readLock();
     private final Lock writeDataLock = dataLock.writeLock();
 
-    private List<T> data;
+    private ImmutableList<T> data;
 
     /**
      * Tells how to load the data.
+     * <p>
+     * Internally will be converted into a {@link ImmutableList}.
+     * </p>
      *
      * @return the loaded data. Never <code>null</code> but could be <i>empty</i>.
      */
-    public abstract List<T> loadData();
+    public abstract Iterable<T> loadData();
 
     private void ensureDataLoaded() {
         LockUtils.runWithLock(writeDataLock, () -> {
             if (data == null) {
-                data = loadData();
+                Iterable<T> data = loadData();
+                if (data instanceof ImmutableList) {
+                    this.data = (ImmutableList<T>) data;
+                } else {
+                    this.data = ImmutableList.copyOf(data);
+                }
             }
         });
     }

src/main/java/org/apache/camel/component/dataprovider/StaticDataProvider.java

@@ -3,29 +3,34 @@
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Range;
 
-import java.util.Arrays;
-import java.util.Collection;
-import java.util.List;
-
 /**
  * {@link IDataProvider} implementation which already specifies all the data in the constructor.
  *
  * @author <a href="mailto:christian.ribeaud@novartis.com">Christian Ribeaud</a>
  */
 public class StaticDataProvider<T> implements IDataProvider<T> {
 
-    private final List<T> data;
+    // Immutable list is expected here
+    private final ImmutableList<T> data;
 
     public StaticDataProvider(T... data) {
-        this(Arrays.asList(data));
+        this(ImmutableList.copyOf(data));
     }
 
-    public StaticDataProvider(Collection<T> data) {
+    /**
+     * Constructor with provided {@link Iterable} <i>data</i>.
+     * <p>
+     * Internally will be converted into a {@link ImmutableList}.
+     * </p>
+     *
+     * @param data the {@link Iterable} data. Can NOT be <code>null</code>.
+     */
+    public StaticDataProvider(Iterable<T> data) {
         assert data != null : "Unspecified data";
-        if (data instanceof List == false) {
+        if (data instanceof ImmutableList == false) {
             this.data = ImmutableList.copyOf(data);
         } else {
-            this.data = ((List<T>) data);
+            this.data = (ImmutableList<T>) data;
         }
     }