ByteBuffer API has been in Java since 1.4. The name itself suggests that these contain bytes of data. The data to be stored in the buffer can be Integer (int, long), Characters (char), Floating value (double), all these are converted into bytes before being stored in the buffer array. ByteBuffer can be of two types-
- Direct ByteBuffer
- Non-Direct ByteBuffer
also read:
- Java Tutorials
- Java EE Tutorials
- Design Patterns Tutorials
- Java File IO Tutorials
Direct ByteBuffer: JVM tries to use Native IO operations on buffers which are created as direct i.e it doesnt load the buffer contents into another buffer and instead tries to use the buffer directly.
There are a few essential properties of ByteBuffer:
- Limit: While writing to a buffer, limit indicates how many more bytes can be written, whereas while reading from a buffer limit indicates how many more bytes can be read.
- Position: Position tracks how much data is written or can be read from a buffer.
- Capacity: Capacity specifies the number of bytes a buffer can store.
ByteBuffer provides plethora of methods to fetch data from the buffer and to add data to the buffer. The below code shows the use of those APIs:
import java.nio.ByteBuffer; public class ByteBufferTest { public static void main(String[] args) { //Create a directBuffer of size 200 bytes ByteBuffer directBuffer = ByteBuffer.allocateDirect(200); //Create a nonDirectBuffer of size 200 bytes ByteBuffer nonDirectBuffer = ByteBuffer.allocate(200); //Get the capacity of the buffer System.out.println("Capacity "+nonDirectBuffer.capacity()); //Get the position of the buffer System.out.println("Position "+nonDirectBuffer.position() ); //Add data of different types to the buffer nonDirectBuffer.putChar('A'); nonDirectBuffer.putInt(10); nonDirectBuffer.putDouble(0.98); //Get the position of the buffer, would print 14 as its has 14 bytes of data System.out.println("Position "+nonDirectBuffer.position() ); nonDirectBuffer.putFloat(8.9f); //Fetch the data from buffer System.out.println(nonDirectBuffer.getChar(0)); //A char is of 2 bytes, so fetch the integer at index 0+2=2bytes System.out.println(nonDirectBuffer.getInt(2)); //A int is of 4 bytes so fetch the double value at index 2+4=6bytes System.out.println(nonDirectBuffer.getDouble(6)); //A double is of 8 bytes so fetch the float value at index 6+8=14bytes System.out.println(nonDirectBuffer.getFloat(14)); } }