JSON to Java Classes Converter

How to Convert JSON to Java Classes

Paste a JSON object or an array of objects into the left pane. The converter parses the JSON in your browser and updates the Java output automatically; there is no separate Convert button.

Choose POJO, Lombok, or Record mode depending on the code style you need, then copy or download the generated draft class. The Try Example button loads a nested sample so you can see how child objects and arrays are handled.

• POJO: Classic Java class with private fields, public getters, and public setters.
• Lombok: Adds @Data, @NoArgsConstructor, and @AllArgsConstructor.
• Java Record: Java 16+ record syntax, immutable, and useful for read-only API response models.

When to Use This Tool

Use this converter when you are exploring an API response, building DTOs for a Java client, or moving from a quick JSON sample to a typed model. It is most useful at the first-draft stage: generate the shape, paste it into your IDE, then add package names, imports, validation annotations, and JSON library annotations as needed.

How It Works

The browser runs JSON.parse(), walks the resulting object, and infers Java field types from the values it finds. Strings become String, integers become int or Integer, decimals become double or Double, booleans become boolean or Boolean, arrays become List<...>, nested objects become nested class definitions, and null values fall back to Object.

All conversion logic runs locally in JavaScript. Your pasted JSON is not uploaded, queued, logged, or sent to a remote conversion service.

Tips, Edge Cases, and Limitations

1. Field names: Simple JSON keys convert cleanly. Keys with spaces, hyphens, or reserved Java words may need manual cleanup or @JsonProperty annotations.

2. Arrays: The converter infers an array type from the first item. Mixed arrays may need a wider type such as List<Object> after review.

3. Numbers: Integer-looking values map to Java integer types; decimal-looking values map to floating-point types. Adjust to long, BigInteger, or BigDecimal when your domain requires it.

4. Dependencies: Lombok mode only emits annotations. Your project still needs the Lombok dependency and IDE annotation-processing support.

5. Compile check: Treat the output as a fast draft, then compile and test it with the JSON library used by your application.

Quick reference

Example walk-through

{
  "name": "John",
  "age": 30,
  "address": { "city": "NYC", "zip": "10001" },
  "hobbies": ["reading"],
  "active": true,
  "score": 9.5,
  "nickname": null
}

public class RootObject {
    private String name;
    private int age;
    private Address address;
    private List<String> hobbies;
    private boolean active;
    private double score;
    private Object nickname;
}

public class Address {
    private String city;
    private String zip;
}