1. Introduction
Converting a short value to a byte array is a common task when dealing with binary data. In this example, I will demonstrate short byte array conversion in the following ways:
- Using java.nio.ByteBuffer‘s array method.
- Using java.io.ByteArrayOutputStream‘s toByteArray method.
- Using the signed right shift operator >>.
2. Setup
In this step, I will create a maven project with the Junit library.
pom.xml
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>org.zheng.demo</groupId> <artifactId>convert_short_to_bytearray</artifactId> <version>0.0.1-SNAPSHOT</version> <build> <plugins> <plugin> <artifactId>maven-compiler-plugin</artifactId> <version>3.8.1</version> <configuration> <release>17</release> </configuration> </plugin> </plugins> </build> <dependencies> <!-- junit 5 --> <dependency> <groupId>org.junit.jupiter</groupId> <artifactId>junit-jupiter-engine</artifactId> <version>5.5.2</version> <scope>test</scope> </dependency> </dependencies> </project>
3. Junit Test Class
In this step, I will convert a short value to a byte array with three tests.
TestConvertShortToByteArray.java
package convert_short_to_bytearray;
import static org.junit.jupiter.api.Assertions.assertArrayEquals;
import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import org.junit.jupiter.api.Test;
public class TestConvertShortToByteArray {
short shortValue = 32767;
byte[] expectedByteArray = { 127, -1 };
@Test
public void convertToByteArray_via_ByteBuffer() {
byte[] byteArray = ByteBuffer.allocate(Short.BYTES).putShort(shortValue).array();
assertArrayEquals(expectedByteArray, byteArray);
}
@Test
public void convertToByteArray_via_DataOutputStream() throws IOException {
try (ByteArrayOutputStream baos = new ByteArrayOutputStream();
DataOutputStream dos = new DataOutputStream(baos)) {
dos.writeShort(shortValue);
byte[] byteArray = baos.toByteArray();
assertArrayEquals(expectedByteArray, byteArray);
}
}
@Test
public void convertToByteArray_via_BitShiftOperator() {
byte[] byteArray = new byte[Short.BYTES];
byteArray[0] = (byte) (shortValue >> 8);
byteArray[1] = (byte) shortValue;
assertArrayEquals(expectedByteArray, byteArray);
}
}
- line 18:
convertToByteArray_via_ByteBuffer– utilizes thejava.nio.ByteBufferclass. See step 3.1 for a detailed explanation. - line 25:
convertToByteArray_via_DataOutputStream– usesjava.io.ByteArrayOutputStreamclass. See step 3.2 for a detailed explanation. - line 37:
convertToByteArray_via_BitShiftOperator– uses the signed right shift operator. See step 3.3 for a detailed explanation.
3.1 Short Byte Array Conversion via ByteBuffer
We will convert a short to a byte array with three steps.
- First, create a
ByteBufferobject with the size ofShort.BYTESviaByteBuffer.allocate(Short.BYTES) - Second, write the given short value via
putShort(shortValue). - Last, invoke the
arraymethod to convert to a byte array.
3.2 Short Byte Array Conversion via ByteArrayOutputStream
Following three steps to convert a short into a byte array.
- First, create a
ByteArrayOutputStreamandDataOutputStreamobjects. - Then write the short value via
dos.writeShort(shortValue). - Finally, convert to a byte array via
baos.toByteArray();
3.3 Short Byte Array Conversion via Bit Shift Operator
A short in Java is a 16-bit signed integer and takes 2 bytes in memory. The first byte stores the high-order bits and the second byte stores the lower-order bits. In this step, I will use the “signed right shift operator” ( >>) to create a byte array from a short value.
- The
shortValue >> 8shifts the bits ofshortValueto the right by 8 positions. This operation effectively isolates the most significant byte of theshortValueas the most significant byte (high-order byte) of a short is stored in the element at index 0 ofbyte[]. - The least significant byte (low-order byte) is stored in the element at index 1 of
byte[]. The(byte)again castsshortValueto abyte, truncating the higher-order bits that do not fit into a byte.
4. Run Test
In this step, I will run the tests and verify the tests are passed.
5. Conclusion
In this example, I demonstrated short byte array conversion in the following ways:
- Using java.nio.ByteBuffer‘s array method.
- Using java.io.ByteArrayOutputStream‘s toByteArray method.
- Using the signed right shift operator >>.
6. Download
This was an example of a maven project which converts a short value into a byte array.
You can download the full source code of this example here: Convert Short to Byte Array
