Perhaps you should try some spelling variations:
"using java core snippets" » "using data core snippets"
"duong cao dan snippets" » "duong co dan snippets", "duong dao dan snippets", "duong cac dan snippets", "duong cao dang snippets", "duong cao danh snippets"
"locating bug code snippets" » "locating bung code snippets", "locating bugs code snippets"

You may be able to get more results by adjusting your search query.

• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"using java core snippets\") OR (\"duong cao dan snippets\"))) OR (\"locating bug code snippets\"))~".
• Removing quotes may allow a broader search: (((( using java core snippets ) OR ( duong cao dan snippets ))) OR ( locating bug code snippets ))~.
• Adding a wildcard symbol may retrieve word variants: (((("using java core snippets") OR ("duong cao dan snippets"))) OR ("locating bug code snippets"))*.