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.
Top answer 1 of 3
3
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.
2 of 3
-1
You have to directly construct JSONArray from JSON string in this case.
JSONArray arr = new JSONArray(jstring);
Mkyong
mkyong.com › home › java › how to parse json array with jackson
How to parse JSON Array with Jackson - Mkyong.com
April 23, 2024 - package com.mkyong.json.jackson; import com.fasterxml.jackson.core.JsonProcessingException; import com.fasterxml.jackson.databind.ObjectMapper; import com.mkyong.json.model.Person; import java.util.Arrays; import java.util.HashMap; import java.util.List; import java.util.Map; public class JsonArrayToObjectExample3 { public static void main(String[] args) throws JsonProcessingException { // Create a list of Person objects List<Person> people = Arrays.asList( new Person("mkyong", 42), new Person("ah pig", 20) ); // Wrap the list in a Map with "Person" as the key Map<String, List<Person>> wrapper
How to convert JSON string into List of Java object? - Stack Overflow
Bring the best of human thought and AI automation together at your work. Explore Stack Internal ... I have this in my String object. Now I want to convert it into Java object and store it in List of java object. e.g. In Student object. More on stackoverflow.com
How to turn json objects into an array of json objects using Java?
Please ensure that: Your code is properly formatted as code block - see the sidebar (About on mobile) for instructions You include any and all error messages in full You ask clear questions You demonstrate effort in solving your question/problem - plain posting your assignments is forbidden (and such posts will be removed) as is asking for or giving solutions. Trying to solve problems on your own is a very important skill. Also, see Learn to help yourself in the sidebar If any of the above points is not met, your post can and will be removed without further warning. Code is to be formatted as code block (old reddit: empty line before the code, each code line indented by 4 spaces, new reddit: https://imgur.com/a/fgoFFis ) or linked via an external code hoster, like pastebin.com, github gist, github, bitbucket, gitlab, etc. Please, do not use triple backticks (```) as they will only render properly on new reddit, not on old reddit. Code blocks look like this: public class HelloWorld { public static void main(String[] args) { System.out.println("Hello World!"); } } You do not need to repost unless your post has been removed by a moderator. Just use the edit function of reddit to make sure your post complies with the above. If your post has remained in violation of these rules for a prolonged period of time (at least an hour), a moderator may remove it at their discretion. In this case, they will comment with an explanation on why it has been removed, and you will be required to resubmit the entire post following the proper procedures. To potential helpers Please, do not help if any of the above points are not met, rather report the post. We are trying to improve the quality of posts here. In helping people who can't be bothered to comply with the above points, you are doing the community a disservice. I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns. More on reddit.com
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4
June 28, 2022api design - Representing a large list of complex objects in JSON - Software Engineering Stack Exchange
I am currently developing an API that returns JSON structures. One of the domain objects returned is a time series, which is a potentially large list (many thousands of elements) of complex objects... More on softwareengineering.stackexchange.com
java - JSON Structure for List of Objects - Stack Overflow
I would like to know, whats the right structure for a list of objects in JSON. We are using JAXB to convert the POJO's to JSON. Here is the choices, Please direct me what is right. foos: [ ... More on stackoverflow.com
Videos
Baeldung
baeldung.com › home › json › jackson › convert json array to java list
Convert JSON Array to Java List | Baeldung
August 13, 2025 - Then, we use the readValue() method of the ObjectMapper object to convert the JSON array String to a List. Similar to the assertion discussed previously, finally, we compare a specific field from the String JSON array to the jacksonList corresponding field. In this article, we discussed how to convert a JSON array to a Java List using two popular libraries: Gson and Jackson.
TutorialsPoint
tutorialspoint.com › convert-a-list-of-objects-to-json-using-the-gson-library-in-java
Convert a list of objects to JSON using the Gson library in Java?
April 22, 2025 - Then, create a list of objects. Then we will create an instance of Gson class. Next, we will convert the list to JSON using the toJson() method of Gson.
Top answer 1 of 11
186
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>>(){});
2 of 11
17
For any one who looks for answer yet:
1.Add jackson-databind library to your build tools like Gradle or Maven
2.in your Code:
ObjectMapper mapper = new ObjectMapper();
List<Student> studentList = new ArrayList<>();
studentList = Arrays.asList(mapper.readValue(jsonStringArray, Student[].class));
How to do in Java
howtodoinjava.com › home › convert json array to list: gson, jackson and org.json
Convert JSON Array to List: Gson, Jackson and Org.json
September 25, 2023 - The following code parses a JSON array containing person data and converts it into a list of Java Person objects using the JSONArray and JSONObject classes.
MuleSoft
help.mulesoft.com › s › question › 0D52T00004mXPbwSAG › convert-json-array-to-java-list-of-objects
Convert json array to java list of objects
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GeeksforGeeks
geeksforgeeks.org › java › how-to-convert-an-arraylist-of-objects-to-a-json-array-in-java
How to Convert an ArrayList of Objects to a JSON Array in Java? - GeeksforGeeks
July 23, 2025 - Here we are adding the logic of converting an ArrayList of objects to a JSON array of Java in the main class. ... package org.example; import com.fasterxml.jackson.core.JsonProcessingException; import com.fasterxml.jackson.databind.ObjectMapper; import java.util.ArrayList; import java.util.List; public class Main { public static void main(String[] args) { // Create an ArrayList of objects List<Course> courses = new ArrayList<>(); courses.add( new Course(1, "Java", "25000", "3 Months")); courses.add( new Course(2, "C++", "20000", "3 Months")); // Convert the ArrayList to a JSON array ObjectMapper objectMapper = new ObjectMapper(); try { String jsonArray = objectMapper.writeValueAsString(courses); System.out.println(jsonArray); } catch (JsonProcessingException e) { e.printStackTrace(); } } }
Java Code Geeks
javacodegeeks.com › home › core java
Converting JSON Array to Java List with Gson - Java Code Geeks
April 25, 2024 - We parse a JSON array into a JsonArray using Gson’s JsonParser. Then, we iterate over each element of the array, converting them into Java objects using Gson’s fromJson() method. Finally, we add each Java object to a List.
TutorialsPoint
tutorialspoint.com › how-can-we-convert-a-json-array-to-a-list-using-jackson-in-java
How can we convert a JSON array to a list using Jackson in Java?\\n
June 5, 2025 - import com.fasterxml.jackson.core.type.TypeReference; import com.fasterxml.jackson.databind.ObjectMapper; import java.util.List; import java.io.IOException; import java.util.ArrayList; public class JsonArrayToList{ public static void main(String[] args) { String jsonArray = "[{"name":"John","age":30},{"name":"Jane","age":25}]"; ObjectMapper objectMapper = new ObjectMapper(); try { List<Person> personList = objectMapper.readValue(jsonArray, new TypeReference<List<Person>>(){}); for (Person person : personList) { System.out.println("Name: " + person.getName() + ", Age: " + person.getAge()); } }
HowToDoInJava
howtodoinjava.com › home › gson › gson – parse json array to java array or list
Gson - Parse JSON Array to Java Array or List
April 4, 2023 - Java program to deserialize JSON array as member object – to Java list of objects a member field.
Quora
quora.com › How-do-I-convert-a-list-to-JSON-in-Java
How to convert a list to JSON in Java - Quora
Answer (1 of 8): Just use ObjectMapper from fasterxml library. [code]import com.fasterxml.jackson.databind.ObjectMapper; ObjectMapper mapper = new ObjectMapper(); String jsonString = mapper.writeValueAsString(anyObject); [/code]
Reddit
reddit.com › r/javahelp › how to turn json objects into an array of json objects using java?
r/javahelp on Reddit: How to turn json objects into an array of json objects using Java?
June 28, 2022 -
Hi. I'm new to java and stuck wondering how I would go about turning something like this: {} {} {} into this: [{},{},{}]. I'm trying to figure out how to do this to my incoming json data using Java. The data has like 20 similar objects, with the same keys but with constantly changing values.
Any help is much appreciated.
Sincerely,
your friendly neighborhood noob
Top answer 1 of 2
4
Look into Collections. you can use a List with List.of(obj1, obj2,...), The return here is going to be immutable and serializable, alternatively Arrays.asList({obj1, obj2,...}). Again, check out java.util.collections for more details
2 of 2
1
Please ensure that: Your code is properly formatted as code block - see the sidebar (About on mobile) for instructions You include any and all error messages in full You ask clear questions You demonstrate effort in solving your question/problem - plain posting your assignments is forbidden (and such posts will be removed) as is asking for or giving solutions. Trying to solve problems on your own is a very important skill. Also, see Learn to help yourself in the sidebar If any of the above points is not met, your post can and will be removed without further warning. Code is to be formatted as code block (old reddit: empty line before the code, each code line indented by 4 spaces, new reddit: https://imgur.com/a/fgoFFis ) or linked via an external code hoster, like pastebin.com, github gist, github, bitbucket, gitlab, etc. Please, do not use triple backticks (```) as they will only render properly on new reddit, not on old reddit. Code blocks look like this: public class HelloWorld { public static void main(String[] args) { System.out.println("Hello World!"); } } You do not need to repost unless your post has been removed by a moderator. Just use the edit function of reddit to make sure your post complies with the above. If your post has remained in violation of these rules for a prolonged period of time (at least an hour), a moderator may remove it at their discretion. In this case, they will comment with an explanation on why it has been removed, and you will be required to resubmit the entire post following the proper procedures. To potential helpers Please, do not help if any of the above points are not met, rather report the post. We are trying to improve the quality of posts here. In helping people who can't be bothered to comply with the above points, you are doing the community a disservice. I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns.
Top answer 1 of 7
2
Lean towards option 1, as it's a more expected format.
Option 1 works with JSON as it's designed to be used and therefore benefits from what JSON offers (a degree of human readability, which is good for debugging, and straightforward parsing, which is good for limiting entire categories of bugs to begin with).
Option 2 begrudgingly adopts JSON and subverts many of the benefits. If you don't want human readability, use protobuf or something similar... AIWalker's "CSV"-like approach isn't terrible either. It is marginally better (readable) than splitting objects apart and recombining them. But, this is still not as good (readable) as using JSON "as designed".
Also bear in mind, your API responses are also likely going to be gzipped. Most of the repetition in option 1 will be quickly and transparently condensed over the wire.
As an aside, if you're moving a lot of data, also consider JSONL or paginated results. Pagination can be especially helpful for web clients, as it places natural pauses in the processing, providing a degree of "organic" protection against UI lockups.
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3
A list of objects is easier to work with. You can use append, map, filter... All the nice things JS Arrays have which manual indexing doesn't. And there's no way to get out of sync, so that's an entire class of bugs gone.
If you're worried about efficiency:
- Measure (premature optimization is the root of all evil)
- Consider the list of lists trick AIWalker proposed
- Consider an outright binary format
- Make sure gzip is enabled
- Measure (it's worth saying twice)
Top answer 1 of 4
123
The second is almost correct:
Copy{
"foos" : [{
"prop1":"value1",
"prop2":"value2"
}, {
"prop1":"value3",
"prop2":"value4"
}]
}
2 of 4
57
The first example from your question,
Copyfoos: [
foo: { ... },
foo: { ... }
]
is in invalid syntax. You cannot have object properties inside a plain array.
The second example from your question,
Copyfoos: [
{ ... },
{ ... }
]
is right although it is not strict JSON. It's a relaxed form of JSON wherein quotes in string keys are omitted.
Following is the correct one when you want to obey strict JSON:
Copy"foos": [
{ ... },
{ ... }
]
This "Mastering JSON" tutorial by Patrick Hunlock, may help to learn about JSON and this site may help to validate JSON.
Attacomsian
attacomsian.com › blog › jackson-convert-json-array-to-from-java-list
Convert JSON array to a list using Jackson in Java
November 6, 2022 - Now we can use the readValue() method from the ObjectMapper class to transform the above JSON array to a list of User objects, as shown below: try { // JSON array String json = "[{\"name\":\"John Doe\",\"email\":\"john.doe@example.com\"," + "\"roles\":[\"Member\",\"Admin\"],\"admin\":true},{\"name\":\"Tom Lee\"," + "\"email\":\"tom.lee@example.com\",\"roles\":[\"Member\"],\"admin\":false}]"; // convert JSON array to Java List List<User> users = new ObjectMapper().readValue(json, new TypeReference<List<User>>() {}); // print list of users users.forEach(System.out::println); } catch (Exception ex) { ex.printStackTrace(); }
Baeldung
baeldung.com › home › java › java list › converting a java list to a json array
Converting a Java List to a Json Array | Baeldung
June 18, 2025 - In the provided code snippet, we instantiate the ObjectMapper class and utilize its writeValueAsString() method. This method allows us to convert the articles List into a JSON array, which is then represented as a string. In addition to external libraries like Gson and Jackson, Java also provides a built-in library called org.json for JSON processing.
JAXB
javaee.github.io › tutorial › jsonp001.html
Introduction to JSON
Arrays are enclosed in brackets ([]), and their values are separated by a comma (,). Each value in an array may be of a different type, including another array or an object. When objects and arrays contain other objects or arrays, the data has a tree-like structure. JSON is often used as a common format to serialize and deserialize data in applications that communicate with each other over the Internet.
Coderanch
coderanch.com › t › 643753 › java › Create-Json-List-data
Create Json from a List's data (EJB and other Jakarta /Java EE Technologies forum at Coderanch)
Something along the lines of: ... All these names though are retrieved from the DB and held in Lists. My first reaction was to iterate the Lists, after specifying an ArrayBuilder outside the loop, and add these objects. Problem is it doesn't work. Either I don't add the elements correctly or it doesn't write the output correctly. How would you write a similar Json iterating a List? Netbeans 11 - JavaEE ...
Baeldung
baeldung.com › home › spring › spring boot › get list of json objects with spring resttemplate
Get list of JSON objects with Spring RestTemplate | Baeldung
December 11, 2025 - In this tutorial, we’ll explore how we can convert a JSON Array into three different object structures in Java: Array of Object, Array of POJO and a List of POJO.