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Difference between concatenating strings and using StringBuffer append
String s = "<span class="className">StaticContent</span>";

String s = "<span class="className">" +
           ResourceBundleObject.getString("StaticContent.key") + "</span>";

StringBuilder sb = new StringBuilder();
sb.append("<span class="className">");
sb.append(ResourceBundleObject.getString("StaticContent.key"));
sb.append("</span>");
String s = sb.toString();

"a" + "b" + "c" + "d"      // 4 Strings
"ab"                       // 1 String
"abc"                      // 1 String
"abcd"                     // 1 String
                           // 7 String instances in total (& in theory / worst case)

StringBuilder sb = new StringBuilder("a").append("b").append("c").append("d")
                           // 4 Strings, 1 StringBuilder
                               = 5 objects (in theory/worst case)

String result = "";
 for (int i = 0; i < 100; i++)
   result += ".";    // Ouch - this should be done with StringBuilder

1. First One will create three Instance.  // "" will create 2 temp instance , concat using + another instance
 2. Second One wil create One Instance.

 - the String class is an immutable class.
 - It will never really change internally. When you use the operator
   it actually  do not change the string itself, but rather return a
   new String.

 - StringBuilder is more efficient as it is designed with no thread-safety in mind.
 - Will appends to it the previous value of the string.
 - if you are building long strings, then using StringBuilder
 - no synchronization is performed.
 - StringBuilder lacks some methods split,search