Add stream support to IStructuredSelection

Streams offer much more flexibility as they can be filtered, mapped and
finally collected to any useful representation of the data.

This adds a new stream() method to IStructuredSelection so consumers of
selections can benefit from this without any additional casting or
boilerplate code (example of code simplification included in this PR),
implement it as a default method for backward compatibility of
implementors and adjust the implementation to return a slightly more
efficient variant.

Author: laeubi

bundles/org.eclipse.jface/.settings/.api_filters

@@ -1,5 +1,21 @@
 <?xml version="1.0" encoding="UTF-8" standalone="no"?>
 <component id="org.eclipse.jface" version="2">
+    <resource path="META-INF/MANIFEST.MF">
+        <filter id="926941240">
+            <message_arguments>
+                <message_argument value="3.32.0"/>
+                <message_argument value="3.31.0"/>
+            </message_arguments>
+        </filter>
+    </resource>
+    <resource path="src/org/eclipse/jface/viewers/IStructuredSelection.java" type="org.eclipse.jface.viewers.IStructuredSelection">
+        <filter id="404000815">
+            <message_arguments>
+                <message_argument value="org.eclipse.jface.viewers.IStructuredSelection"/>
+                <message_argument value="stream()"/>
+            </message_arguments>
+        </filter>
+    </resource>
     <resource path="src/org/eclipse/jface/viewers/ViewerCell.java" type="org.eclipse.jface.viewers.ViewerCell">
         <filter comment="constants should be final" id="388100214">
             <message_arguments>

bundles/org.eclipse.jface/META-INF/MANIFEST.MF

@@ -2,7 +2,7 @@ Manifest-Version: 1.0
 Bundle-ManifestVersion: 2
 Bundle-Name: %pluginName
 Bundle-SymbolicName: org.eclipse.jface;singleton:=true
-Bundle-Version: 3.31.100.qualifier
+Bundle-Version: 3.32.0.qualifier
 Bundle-Vendor: %providerName
 Bundle-Localization: plugin
 Export-Package: org.eclipse.jface,

bundles/org.eclipse.jface/src/org/eclipse/jface/dialogs/AbstractSelectionDialog.java

@@ -220,7 +220,7 @@ protected void setResult(ISelection selection, Class<T> target) {
 		List<T> selected = null;
 		if (selection instanceof IStructuredSelection && target != null) {
 			IStructuredSelection structured = (IStructuredSelection) selection;
-			selected = ((List<?>) structured.toList()).stream().filter(target::isInstance)
+			selected = structured.stream().filter(target::isInstance)
 					.map(target::cast).collect(Collectors.toList());
 		}
 		setResult(selected);

bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/IStructuredSelection.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2000, 2015 IBM Corporation and others.
+ * Copyright (c) 2000, 2023 IBM Corporation and others.
  *
  * This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License 2.0
@@ -10,11 +10,14 @@
  *
  * Contributors:
  *     IBM Corporation - initial API and implementation
+ *     Christoph Läubrich - add support for stream() method
  *******************************************************************************/
 package org.eclipse.jface.viewers;
 
 import java.util.Iterator;
 import java.util.List;
+import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
 
 /**
  * A selection containing elements.
@@ -57,4 +60,15 @@ public interface IStructuredSelection extends ISelection, Iterable {
 	 * @return the selected elements as a list
 	 */
 	public List toList();
+
+	/**
+	 * Returns the elements in this selection as a <code>Stream</code>.
+	 *
+	 * @return the selected elements as a stream
+	 * @since 3.32
+	 */
+	@SuppressWarnings("unchecked")
+	default Stream<Object> stream() {
+		return StreamSupport.stream(spliterator(), false);
+	}
 }

bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/StructuredSelection.java

@@ -18,6 +18,7 @@
 import java.util.Iterator;
 import java.util.List;
 import java.util.Objects;
+import java.util.stream.Stream;
 
 import org.eclipse.core.runtime.Assert;
 import org.eclipse.jface.resource.JFaceResources;
@@ -207,6 +208,14 @@ public List toList() {
 		return Arrays.asList(elements == null ? new Object[0] : elements);
 	}
 
+	@Override
+	public Stream<Object> stream() {
+		if (isEmpty()) {
+			return Stream.empty();
+		}
+		return Arrays.stream(elements);
+	}
+
 	/**
 	 * Internal method which returns a string representation of this
 	 * selection suitable for debug purposes only.
@@ -215,6 +224,7 @@ public List toList() {
 	 */
 	@Override
 	public String toString() {
-		return isEmpty() ? JFaceResources.getString("<empty_selection>") : toList().toString(); //$NON-NLS-1$
+		return isEmpty() ? JFaceResources.getString("<empty_selection>") //$NON-NLS-1$
+				: Arrays.toString(elements);
 	}
 }