How to Convert a JSON Object to Long in Java

Описание: Learn how to effectively convert a JSON object to a `long` in Java, avoiding data overflow issues related to `int` conversions.
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This video is based on the question https://stackoverflow.com/q/74135898/ asked by the user 'Zosmack' ( https://stackoverflow.com/u/20132756/ ) and on the answer https://stackoverflow.com/a/74136259/ provided by the user 'dengsl' ( https://stackoverflow.com/u/20287715/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Convert a JSON Object to Long in Java: A Simple Guide

If you are working with JSON objects in Java, you might encounter a challenge when trying to convert a large number from a JSON object into an int. This is because Java's int type has a maximum value of 2,147,483,647. If you're dealing with data that exceeds this number, like timestamps or large integer values, converting it directly to an int can lead to unexpected results and overflow errors. In this post, we'll dive into a specific example of this issue and how to correctly convert a JSON object field to a long type to avoid these pitfalls.

The Problem

You have a JSON object that looks like this:

[[See Video to Reveal this Text or Code Snippet]]

When you try to retrieve the value associated with the key "date" as an int, you encounter two different outputs:

The correct value: 1665750692735 (the expected long value)

The incorrect, overflowed value: -696618113

This inconsistency arises because the value you're trying to pull is too large for an int to handle, causing it to overflow.

Understanding the Cause of Overflow

The Java programming language provides several types of numerical data types, including:

byte: 8 bits

short: 16 bits

int: 32 bits

long: 64 bits

The int type cannot accurately represent values larger than 2,147,483,647. When a number larger than this limit is cast to int, it wraps around and returns a negative value or a completely different number. This is known as a data overflow.

For example:

Value: 1665750692735 (larger than int maximum)

Attempting to convert yields incorrect results due to overflow.

The Solution: Convert to Long instead

To address this problem, you should retrieve the value as a long type from the JSON object. Here's how to do it:

Modify Your Method: Change the method that retrieves the value from int to long. This ensures that you avoid overflow errors since long can handle larger values.

Use getAsJsonPrimitive: When working with JSON objects, use the appropriate method to extract the value based on its type.

Updated Method Example

Here's how the updated method might look:

[[See Video to Reveal this Text or Code Snippet]]

In this updated example:

getAsLong() correctly retrieves the value as a long, preventing any overflow issues.

You can also retrieve the name field as a String without issues, as it’s not a large numerical value.

Conclusion

When working with JSON in Java, always be mindful of the data types you're retrieving. If you expect large numbers, opt for the long type over int to maintain data integrity and prevent overflow errors. Making this small adjustment can save you a lot of confusion and debugging time in your applications.

By following these steps, you can ensure that you accurately handle large numeric values and their representation in your Java applications. Happy coding!