String s = \"m\\\\\"+\"/m\\\\/m/m/m/m/m\";
    LinkedHashMap hm = new LinkedHashMap<>();
    hm.put(\"test\", s);
    System.out.p         
         Since some people like to nitpick, I'll add the answer to the question (even though it was already answered and chosen as the correct answer) ...
I agree with the chose answer to this question, use the following code:
Gson gson = new GsonBuilder().disableHtmlEscaping().create();
String s2 = gson.toJson(hm.toString());
s2.replace("\\\\", "\\");
@Bajrang Hudda has asked about \n ... I hit this issue recently ... I was able to solve it using:
Gson gson = new Gson();
String json = (gson.toJson(data)).replaceAll("\\\\n", "\\n");
The = sign is encoded to \u003d. Hence you need to use disableHtmlEscaping().
You can use
Gson gson = new GsonBuilder().disableHtmlEscaping().create();
String s2 = gson.toJson(hm.toString());
For \/ turning into \\/ issue, the solution is 
s2.replace("\\\\", "\\");