How to Convert a Java Byte Array to a String and Back?

Java Byte Array to String and Back to Byte Array

In Java, converting a byte array to a string is a common task. However, it's crucial to understand that this involves two operations: converting a byte array to a string representation and then back to a byte array. This article aims to clarify this process.

Conversion from Byte Array to String

The Arrays.toString() method is commonly used to obtain a string representation of a byte array. For example, if we have a byte array data containing values [-47, 1, 16, 84, 2, 101, 110, 83, 111, 109, 101, 32, 78, 70, 67, 32, 68, 97, 116, 97], calling Arrays.toString(data.toByteArray()) would yield:

[-47, 1, 16, 84, 2, 101, 110, 83, 111, 109, 101, 32, 78, 70, 67, 32, 68, 97, 116, 97]

This string representation can be sent over a network or stored in a database.

Conversion from String Back to Byte Array

When receiving the string representation on the receiving end, it's necessary to convert it back into a byte array. This involves parsing the string and reconstructing the byte array.

One way to approach this is to use the byteValues() method, which takes a string like "[-47, 1, 16, 84, 2, 101, 110, 83, 111, 109, 101, 32, 78, 70, 67, 32, 68, 97, 116, 97]" and returns an array of strings:

[-47, 1, 16, 84, 2, 101, 110, 83, 111, 109, 101, 32, 78, 70, 67, 32, 68, 97, 116, 97]

Each element in this array represents a byte value. To convert this back to a byte array, you can use a loop to iterate over the strings, parse them to bytes, and store them in a new byte array.

Example Code

The following Python script illustrates the server-side handling of the data received from the client:

response = "[-47, 1, 16, 84, 2, 101, 110, 83, 111, 109, 101, 32, 78, 70, 67, 32, 68, 97, 116, 97]"      # Placeholder response from the client

byte_values = response.substring(1, response.length() - 1).split(",")
# Convert the string values to bytes
bytes = bytearray([int(byte_value.strip()) for byte_value in byte_values])

# Send the bytes back to the client

Note:

Remember that when Arrays.toString() converts a byte array to a string, it loses the original data type information. Therefore, to correctly convert the string back to a byte array, you need to parse the string carefully and manually reconstruct the byte array using the appropriate methods.

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