Index: trunk/src/org/openstreetmap/josm/gui/io/AbstractUploadTask.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/io/AbstractUploadTask.java	(revision 2847)
+++ trunk/src/org/openstreetmap/josm/gui/io/AbstractUploadTask.java	(revision 2848)
@@ -63,5 +63,5 @@
         OsmPrimitive p = layer.data.getPrimitiveById(id, type);
         if (p == null)
-            throw new IllegalStateException(tr("Failed to update primitive with id {0} because current edit layer doesn't include such a primitive", id));
+            throw new IllegalStateException(tr("Failed to update primitive with id {0} because current edit layer does not include such a primitive", id));
         Main.worker.execute(new UpdatePrimitivesTask(layer, Collections.singleton(p)));
     }
@@ -192,5 +192,5 @@
      */
     protected void handleUploadConflictForClosedChangeset(long changsetId, Date d) {
-        String msg =  tr("<html>Uploading <strong>failed</strong> because you''ve been using<br>"
+        String msg =  tr("<html>Uploading <strong>failed</strong> because you have been using<br>"
                 + "changeset {0} which was already closed at {1}.<br>"
                 + "Please upload again with a new or an existing open changeset.</html>",
Index: trunk/src/org/openstreetmap/josm/gui/io/CredentialDialog.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/io/CredentialDialog.java	(revision 2847)
+++ trunk/src/org/openstreetmap/josm/gui/io/CredentialDialog.java	(revision 2848)
@@ -238,6 +238,6 @@
             tfPassword.setToolTipText(tr("Please enter the password name of your OSM account"));
             lblHeading.setText(
-                    tr("<html>Authenticating at the OSM API ''{0}'' failed. Please enter a valid username and a valid password.</html>",
-                            OsmApi.getOsmApi().getBaseUrl()));
+                    "<html>" + tr("Authenticating at the OSM API ''{0}'' failed. Please enter a valid username and a valid password.",
+                            OsmApi.getOsmApi().getBaseUrl()) + "</html>");
             lblWarning.setText(tr("Warning: The password is transferred unencrypted."));
         }
@@ -255,7 +255,7 @@
             tfPassword.setToolTipText(tr("Please enter the password for authenticating at your proxy server"));
             lblHeading.setText(
-                    tr("<html>Authenticating at the HTTP proxy ''{0}'' failed. Please enter a valid username and a valid password.</html>",
-                            System.getProperty("http.proxyHost") + ":" + System.getProperty("http.proxyPort")));
-            lblWarning.setText(tr("<html>Warning: depending on the authentication method the proxy server uses the password may be transferred unencrypted.</html>"));
+                    "<html>" + tr("Authenticating at the HTTP proxy ''{0}'' failed. Please enter a valid username and a valid password.",
+                            System.getProperty("http.proxyHost") + ":" + System.getProperty("http.proxyPort")) + "</html>");
+            lblWarning.setText("<html>" + tr("Warning: depending on the authentication method the proxy server uses the password may be transferred unencrypted.") + "</html>");
         }
 
Index: trunk/src/org/openstreetmap/josm/gui/io/DownloadOpenChangesetsTask.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/io/DownloadOpenChangesetsTask.java	(revision 2847)
+++ trunk/src/org/openstreetmap/josm/gui/io/DownloadOpenChangesetsTask.java	(revision 2848)
@@ -61,10 +61,9 @@
             JOptionPane.showMessageDialog(
                     JOptionPane.getFrameForComponent(parent),
-                    tr("<html>Could not retrieve the list of your open changesets because<br>"
-                            + "JOSM doesn't know your identity.<br>"
-                            + "You've either chosen to work anonymously or you are not entitled<br>"
-                            + "to know the identity of the user on whose behalf you are working."
-                            + "</html>"
-                    ),
+                    "<html>" + tr("Could not retrieve the list of your open changesets because<br>"
+                            + "JOSM does not know your identity.<br>"
+                            + "You have either chosen to work anonymously or you are not entitled<br>"
+                            + "to know the identity of the user on whose behalf you are working.")
+                            + "</html>",
                     tr("Missing user identity"),
                     JOptionPane.ERROR_MESSAGE
Index: trunk/src/org/openstreetmap/josm/gui/io/SaveLayerInfo.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/io/SaveLayerInfo.java	(revision 2847)
+++ trunk/src/org/openstreetmap/josm/gui/io/SaveLayerInfo.java	(revision 2848)
@@ -5,4 +5,6 @@
 
 import org.openstreetmap.josm.gui.layer.OsmDataLayer;
+import org.openstreetmap.josm.tools.CheckParameterUtil;
+
 import static org.openstreetmap.josm.tools.I18n.tr;
 
@@ -28,6 +30,5 @@
      */
     public SaveLayerInfo(OsmDataLayer layer) {
-        if (layer == null)
-            throw new IllegalArgumentException(tr("Parameter ''{0}'' must not be null.", "layer"));
+        CheckParameterUtil.ensureParameterNotNull(layer, "layer");
         this.layer = layer;
         this.doSaveToFile = layer.requiresSaveToFile();
Index: trunk/src/org/openstreetmap/josm/gui/io/SaveLayerTask.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/io/SaveLayerTask.java	(revision 2847)
+++ trunk/src/org/openstreetmap/josm/gui/io/SaveLayerTask.java	(revision 2848)
@@ -7,4 +7,5 @@
 import org.openstreetmap.josm.gui.progress.NullProgressMonitor;
 import org.openstreetmap.josm.gui.progress.ProgressMonitor;
+import org.openstreetmap.josm.tools.CheckParameterUtil;
 
 /**
@@ -35,6 +36,5 @@
      */
     protected SaveLayerTask(SaveLayerInfo layerInfo, ProgressMonitor monitor) {
-        if (layerInfo == null)
-            throw new IllegalArgumentException(tr("Parameter ''{0}'' must not be null.", "layerInfo"));
+        CheckParameterUtil.ensureParameterNotNull(layerInfo, "layerInfo");
         if (monitor == null) {
             monitor = NullProgressMonitor.INSTANCE;
Index: trunk/src/org/openstreetmap/josm/gui/io/SaveLayersDialog.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/io/SaveLayersDialog.java	(revision 2847)
+++ trunk/src/org/openstreetmap/josm/gui/io/SaveLayersDialog.java	(revision 2848)
@@ -487,5 +487,5 @@
             int numProblems = model.getNumCancel() + model.getNumFailed();
             if (numProblems == 0) return;
-            String msg = tr(
+            String msg = trn(
                     "<html>An upload and/or save operation of one layer with modifications<br>"
                     + "was cancelled or has failed.</html>",
Index: trunk/src/org/openstreetmap/josm/gui/io/UploadLayerTask.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/io/UploadLayerTask.java	(revision 2847)
+++ trunk/src/org/openstreetmap/josm/gui/io/UploadLayerTask.java	(revision 2848)
@@ -20,4 +20,5 @@
 import org.openstreetmap.josm.io.OsmServerWriter;
 import org.openstreetmap.josm.io.OsmTransferException;
+import org.openstreetmap.josm.tools.CheckParameterUtil;
 
 /**
@@ -56,8 +57,6 @@
      */
     public UploadLayerTask(UploadStrategySpecification strategy, OsmDataLayer layer, ProgressMonitor monitor, Changeset changeset) {
-        if (layer == null)
-            throw new IllegalArgumentException(tr("Parameter ''{0}'' must not be null.", "layer"));
-        if (strategy == null)
-            throw new IllegalArgumentException(tr("Parameter ''{0}'' must not be null.", "strategy"));
+        CheckParameterUtil.ensureParameterNotNull(layer, "layer");
+        CheckParameterUtil.ensureParameterNotNull(strategy, "strategy");
         if (monitor == null) {
             monitor = NullProgressMonitor.INSTANCE;
Index: trunk/src/org/openstreetmap/josm/gui/io/UploadStrategySelectionPanel.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/io/UploadStrategySelectionPanel.java	(revision 2847)
+++ trunk/src/org/openstreetmap/josm/gui/io/UploadStrategySelectionPanel.java	(revision 2848)
@@ -322,5 +322,5 @@
             lbl.setIcon(ImageProvider.get("warning-small.png"));
             lbl.setText(tr("Upload in one request not possible (too many objects to upload)"));
-            lbl.setToolTipText(tr("<html>Can''t upload {0} objects in one request because the<br>"
+            lbl.setToolTipText(tr("<html>Cannot upload {0} objects in one request because the<br>"
                     + "max. changeset size {1} on server ''{2}'' is exceeded.</html>",
                     numUploadedObjects,
