Use Paths util to concatenate url

Author: bitwiseman

src/main/java/org/jenkinsci/plugins/workflow/cps/SnippetizerLink.java

@@ -35,6 +35,7 @@
 
 import java.net.URI;
 import java.net.URISyntaxException;
+import java.nio.file.Paths;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
@@ -80,7 +81,7 @@ public final String getDisplayUrl() {
 
         Item i = req.findAncestorObject(Item.class);
 
-        return req.getContextPath() + '/' + (i == null ? "" : i.getUrl()) + u;
+        return Paths.get( req.getContextPath(), i == null ? "" : i.getUrl(), u).toString();
     }
 
     /**