How do you convert integers to byte arrays and vice versa in Java?

Converting Integers to Byte Arrays and Vice Versa in Java

Storing numbers in byte arrays is a fundamental operation in programming. Understanding the conversion process between integers and byte arrays is essential for manipulating data efficiently.

Integer to Byte Array

To convert an integer into a byte array, you can use ByteBuffer, a class from the java.nio package. This class provides a convenient way to interact with binary data. Here's an example:

<code class="java">byte[] arr = { 0x00, 0x01 }; // Source byte array
short num = 0;

ByteBuffer wrapped = ByteBuffer.wrap(arr); // Wraps source array in a buffer
wrapped.get(num); // Reads 2 bytes from the buffer and stores in num</code>

This code wraps the source byte array in a ByteBuffer and reads the first two bytes (0x00 and 0x01) into a short integer (num).

Byte Array to Integer

To convert a byte array back into an integer, you can use the same ByteBuffer class. Here's an example:

<code class="java">byte[] arr = { 0x00, 0x01 };
ByteBuffer dbuf = ByteBuffer.allocate(2);
dbuf.put(arr); // Writes source bytes to the buffer
short num = dbuf.getShort(); // Reads 2 bytes from the buffer and stores in num </code>

This code writes the source byte array to a ByteBuffer, then reads the first two bytes (0x00 and 0x01) into a short integer (num).

Understanding the Code

The key to understanding the ByteBuffer class is that it uses a byte order (big-endian or little-endian) to determine the arrangement of bytes in the array. Big-endian means the most significant byte is stored at the beginning of the array, while little-endian stores it at the end.

By default, the ByteBuffer uses big-endian byte order. You can specify little-endian order by calling wrapped.order(ByteOrder.LITTLE_ENDIAN) before performing any operations.

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