use String.intern() instead of a homebrew equivalent

core/java/src/net/i2p/data/RouterAddress.java

@@ -215,12 +215,8 @@ public class RouterAddress extends DataStructureImpl {
         _cost = (int) DataHelper.readLong(in, 1);
         //_expiration = DataHelper.readDate(in);
         DataHelper.readDate(in);
-        _transportStyle = DataHelper.readString(in);
         // reduce Object proliferation
-        if (_transportStyle.equals("SSU"))
-            _transportStyle = "SSU";
-        else if (_transportStyle.equals("NTCP"))
-            _transportStyle = "NTCP";
+        _transportStyle = DataHelper.readString(in).intern();
         DataHelper.readProperties(in, _options);
     }