Java insert text line above specifice text in string from file with string indentation

i have simple text im reading from file and I'm getting its content as string

String pomxml = "c:\\foo\\test.json";
String content = FileUtils.readFileToString(file); 

the string content (example) is :

"email_settings": {
	  "email.starttls.enable":"true",
	  "email.port":"111",
	  "email.host":"xxxx",
	  "email.auth":"true",
}

i like to insert new string above "email.host":"xxxx", only if it finds it.
so it will look like :

"email_settings": {
	  "email.starttls.enable":"true",
	  "email.port":"111",
	  "email.name":"myTest",
	  "email.host":"xxxx",
	  "email.auth":"true",
}

My question is how to insert this new line into the string

UPDATE
in this example it is JSON , but it can be also simple text or XML file
so i can't rely on JSON providers

You could try doing a regex replacement here:

String input = "\"email_settings\": {\n      \"email.starttls.enable\":\"true\",\n      \"email.port\":\"111\",\n      \"email.host\":\"xxxx\",\n      \"email.auth\":\"true\",\n}";
String output = input.replaceAll("([ ]*\"email.host\":\".*?\")", "      \"email.name\":\"myTest\",\n$1");
System.out.println(output);

This prints:

"email_settings": {
	  "email.starttls.enable":"true",
	  "email.port":"111",
	  "email.name":"myTest",
	  "email.host":"xxxx",
	  "email.auth":"true",
}

However, if you are dealing with proper JSON content, then you should consider using a JSON parser instead. Parse the JSON text into a Java POJO and then write out with the new field.

content = content.replace("\"email.host\":", "\"email.name\":\"myTest\",\n" + "      \"email.host\":");

Or you could look in to libraries which parse json files.