Use GSON library for that. Here is the sample code

List<String> foo = new ArrayList<String>();
foo.add("A");
foo.add("B");
foo.add("C");

String json = new Gson().toJson(foo );

Here is the maven dependency for Gson

<dependencies>
    <!--  Gson: Java to Json conversion -->
    <dependency>
        <groupId>com.google.code.gson</groupId>
        <artifactId>gson</artifactId>
        <version>2.2.2</version>
        <scope>compile</scope>
    </dependency>
</dependencies>

Or you can directly download jar from here and put it in your class path

http://code.google.com/p/google-gson/downloads/detail?name=gson-1.0.jar&can=4&q=

To send Json to client you can use spring or in simple servlet add this code

response.getWriter().write(json);

Call getJSONObject() instead of getString(). That will give you a handle on the JSON object in the array and then you can get the property off of the object from there.

For example, to get the property "value" from a List<SomeClass> where SomeClass has a String getValue() and setValue(String value):

JSONObject obj = new JSONObject();
List<SomeClass> sList = new ArrayList<SomeClass>();

SomeClass obj1 = new SomeClass();
obj1.setValue("val1");
sList.add(obj1);

SomeClass obj2 = new SomeClass();
obj2.setValue("val2");
sList.add(obj2);

obj.put("list", sList);

JSONArray jArray = obj.getJSONArray("list");
for(int ii=0; ii < jArray.length(); ii++)
  System.out.println(jArray.getJSONObject(ii).getString("value"));

You are asking Jackson to parse a StudentList. Tell it to parse a List (of students) instead. Since List is generic you will typically use a TypeReference

List<Student> participantJsonList = mapper.readValue(jsonString, new TypeReference<List<Student>>(){});

You cannot convert this json to List but you can convert this to Map.
See your json String:

...
"Example": [
        {
            "foo": "a1",
            "bar": "b1",
            "fubar": "c1"
        },
        {
            "foo": "a2",
            "bar": "b2",
            "fubar": "c2"
        },
        ...
]
}

Here "Example" is key(String) and value is List object of Example.

Try this:

 parser.addTypeHint("Example[]", Example.class);
 Map<String,List<Example>> result1 = parser.parse(Map.class, json);
 for (Entry<String, List<Example>> entry : result1.entrySet()) {
     for (Example example : entry.getValue()) {
          System.out.println("VALUE :->"+ example.getFoo());
     }
 }

Full code of Example:

import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

import org.svenson.JSONParser;

public class Test {
    public static void main(String[] args) {
        JSONParser parser = new JSONParser();
        parser.addTypeHint(".Example[]", Example.class);
        String json = "{" + "\"Example\": [" + "{" + "\"foo\": \"a1\","
                + "\"bar\": \"b1\"," + "\"fubar\": \"c1\"" + "}," + "{"
                + "\"foo\": \"a2\"," + "\"bar\": \"b2\"," + "\"fubar\": \"c2\""
                + "}," + "{" + "\"foo\": \"a3\"," + "\"bar\": \"b3\","
                + "\"fubar\": \"c3\"" + "}" + "]" + "}\"";
        parser.addTypeHint("Example[]", Example.class);
        Map<String, List<Example>> result1 = parser.parse(Map.class, json);
        for (Entry<String, List<Example>> entry : result1.entrySet()) {
            for (Example example : entry.getValue()) {
                System.out.println("VALUE :->" + example.getFoo());
            }
        }
    }
}

public class Example {
    private String foo;
    private String bar;
    private String fubar;
    public Example(){}
    public void setFoo(String foo) {
        this.foo = foo;
    }
    public String getFoo() {
        return foo;
    }
    public void setBar(String bar) {
        this.bar = bar;
    }
    public String getBar() {
        return bar;
    }
    public void setFubar(String fubar) {
        this.fubar = fubar;
    }
    public String getFubar() {
        return fubar;
    }
}

OutPut:

VALUE :->a1
VALUE :->a2
VALUE :->a3

Using gson it is much simpler. Use following code snippet:

 // create a new Gson instance
 Gson gson = new Gson();
 // convert your list to json
 String jsonCartList = gson.toJson(cartList);
 // print your generated json
 System.out.println("jsonCartList: " + jsonCartList);

Converting back from JSON string to your Java object

 // Converts JSON string into a List of Product object
 Type type = new TypeToken<List<Product>>(){}.getType();
 List<Product> prodList = gson.fromJson(jsonCartList, type);

 // print your List<Product>
 System.out.println("prodList: " + prodList);

Your root JSON is an Array, so first create a JSONArray from your String.

Do this:

JSONArray arr = new JSONArray(jstring);
for (int i = 0; i < arr.length(); i++) { // Walk through the Array.
    JSONObject obj = arr.getJSONObject(i);
    JSONArray arr2 = obj.getJSONArray("fileName");
    // Do whatever.
}

For more info, please refer to the docs on JSONArray and JSONObject.