source: josm/src/org/openstreetmap/josm/command/ChangePropertyCommand.java@ 106

package org.openstreetmap.josm.command;

import static org.openstreetmap.josm.tools.I18n.tr;
import static org.openstreetmap.josm.tools.I18n.trn;

import java.util.Collection;
import java.util.LinkedList;
import java.util.List;

import javax.swing.JLabel;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.MutableTreeNode;

import org.openstreetmap.josm.data.osm.OsmPrimitive;
import org.openstreetmap.josm.data.osm.visitor.NameVisitor;
import org.openstreetmap.josm.tools.ImageProvider;

/**
 * Command that manipulate the key/value structure of several objects. Manages deletion,
 * adding and modify of values and keys.
 * 
 * @author imi
 */
public class ChangePropertyCommand extends Command {
        /**
         * All primitives, that are affected with this command.
         */
        private final List<OsmPrimitive> objects;
        /**
         * The key that is subject to change.
         */
        private final String key;
        /**
         * The key value. If it is <code>null</code>, delete all key references with the given
         * key. Else, change the properties of all objects to the given value or create keys of
         * those objects that do not have the key yet.
         */
        private final String value;
        
        public ChangePropertyCommand(Collection<OsmPrimitive> objects, String key, String value) {
                this.objects = new LinkedList<OsmPrimitive>(objects);
                this.key = key;
                this.value = value;
        }
        
        @Override public void executeCommand() {
                super.executeCommand(); // save old
                if (value == null) {
                        for (OsmPrimitive osm : objects) {
                                osm.modified = true;
                                osm.remove(key);
                        }
                } else {
                        for (OsmPrimitive osm : objects) {
                                osm.modified = true;
                                osm.put(key, value);
                        }
                }
        }

        @Override public void fillModifiedData(Collection<OsmPrimitive> modified, Collection<OsmPrimitive> deleted, Collection<OsmPrimitive> added) {
                modified.addAll(objects);
        }

        @Override public MutableTreeNode description() {
                String text = value == null ? tr( "Remove \"{0}\" for", key) : tr("Set {0}={1} for",key,value);
                if (objects.size() == 1) {
                        NameVisitor v = new NameVisitor();
                        objects.iterator().next().visit(v);
                        text += " "+v.className+" "+v.name;
                } else
                        text += objects.size()+trn("object","objects",objects.size());
                DefaultMutableTreeNode root = new DefaultMutableTreeNode(new JLabel(text, ImageProvider.get("data", "key"), JLabel.HORIZONTAL));
                if (objects.size() == 1)
                        return root;
                NameVisitor v = new NameVisitor();
                for (OsmPrimitive osm : objects) {
                        osm.visit(v);
                        root.add(new DefaultMutableTreeNode(v.toLabel()));
                }
                return root;
    }
}