convert json object to string + java code example

Example 1: how to convert jsonobject to string in java

JSONObject json = new JSONObject();

json.toString();

Example 2: convert java object to json

Jackson Data-bind depdendency that take care of 
Converting between 
JSON to Java Object 
and 
Java Object to JSON

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.12.0</version>
</dependency>