Use StringBuilder in XMLWriter

Done with JDT UI cleanup action.

Change-Id: I3b3a3c01105987fb4b80a452d2d0cb95597cd0c6
Signed-off-by: Lars Vogel <Lars.Vogel@vogella.com>
Reviewed-on: https://git.eclipse.org/r/c/equinox/rt.equinox.p2/+/183163
Tested-by: Equinox Bot <equinox-bot@eclipse.org>
Reviewed-by: Alexander Kurtakov <akurtako@redhat.com>
diff --git a/bundles/org.eclipse.equinox.p2.repository/src/org/eclipse/equinox/internal/p2/persistence/XMLWriter.java b/bundles/org.eclipse.equinox.p2.repository/src/org/eclipse/equinox/internal/p2/persistence/XMLWriter.java
index a31a751..cfcd0bb 100644
--- a/bundles/org.eclipse.equinox.p2.repository/src/org/eclipse/equinox/internal/p2/persistence/XMLWriter.java
+++ b/bundles/org.eclipse.equinox.p2.repository/src/org/eclipse/equinox/internal/p2/persistence/XMLWriter.java
@@ -122,7 +122,7 @@
 	}
 
 	public static String escape(String txt) {
-		StringBuffer buffer = null;
+		StringBuilder buffer = null;
 		for (int i = 0; i < txt.length(); ++i) {
 			String replace;
 			char c = txt.charAt(i);
@@ -162,7 +162,7 @@
 					replace = Character.isWhitespace(c) ? " " : null; //$NON-NLS-1$
 			}
 			if (buffer == null) {
-				buffer = new StringBuffer(txt.length() + 16);
+				buffer = new StringBuilder(txt.length() + 16);
 				buffer.append(txt.substring(0, i));
 			}
 			if (replace != null)