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Mar 6, 2011 · The true reasons for why we need ByteBuffer are two fold: 1) Direct memory access. This means when used in direct mode, ByteBuffer can bypass the JVM garbage collection, and the memory used by ByteBuffer is completely outside the JVM memory pool. 2) Interfacing, as byte [] is primitive and cannot be used in OO way.
Aug 10, 2024 · byte[] bytes = new byte[10];ByteBuffer buffer = ByteBuffer.wrap(bytes); The above code is equivalent to: ByteBuffer buffer = ByteBuffer.wrap(bytes, 0, bytes.length); Any changes made to the data elements in the existing bytearray will be reflected in the buffer instance and vice versa. 2.3.
- Sen Liu
The ByteBuffer class is important because it forms a basis for the use of channels in Java. ByteBuffer class defines six categories of operations upon byte buffers, as stated in the Java 7 documentation: Methods for compacting, duplicating, and slicing a byte buffer. Example code : Putting Bytes into a buffer.
Jan 8, 2024 · When converting an int or a long value to a byte array, we can use the same code snippet: byte[] bytes = BigInteger.valueOf(value).toByteArray(); However, the toByteArray() method of the BigInteger class returns the minimum number of bytes, not necessarily four or eight bytes. 4.2. Byte Array to float and double
- The ByteBuffer Abstraction
- Key Differences from Byte Arrays
- Key Properties of A ByteBuffer
- The Buffer/Stream Duality of Byte Buffers
- Don’T Consume The Buffer
- Don’T Mutate The Buffer
- CompareTo() Is Subject to Byte Signedness
- Array() Is Usually The Wrong Method to Use
Look at a ByteBuffer as providing a viewinto some (undefined) underlying storage of bytes. The two most common concrete types of byte buffers are those backed by byte arrays, and those backed by direct (off-heap, native) byte buffers. In both cases, the same interface can be used to read and write contents of the buffer. Some parts of the API of a ...
A ByteBuffer has value semantics with respect to hashCode()/equals()and as a result can be more conveniently used in containers.A ByteBuffer has offers the ability to pass around a subsetof a byte buffer as a value without copying the bytes, by instantiating a new ByteBuffer.The NIO API makes extensive use of ByteBuffer:s.The bytes in a ByteBuffer may potentially reside outside of the Java heap.The following three properties of a ByteBuffer are critical (I’m quoting the API documentation on each): 1. A buffer’s capacityis the number of elements it contains. The capacity of a buffer is never negative and never changes. 2. A buffer’s limitis the index of the first element that should not be read or written. A buffer’s limit is never negativ...
There are two ways of accessing the contents of a byte buffer – absolute and relativeaccess. For example, suppose I have a ByteBuffer that I know contains two integers. In order to extract the integers using absolute positioning, one might do this: Alternatively one can extract them using relative positioning: The second option is often convenient,...
Be careful not to “consume” a byte buffer when reading it, unless you specifically intend on doing so. For example, consider this method to convert a ByteBuffer into a String, assuming default encoding: Unfortunately, there is no method provided to do absolute positioning reads of a byte array (but there does exist absolute positioning reads for th...
In the context of general-purpose code which is not intimately specific to a particular use-case, it is (in my opinion) good practice for a method that does an (abstractly) read-only operation (such as reading a byte buffer), to not mutate its input. This is a stronger requirement than “Don’t consume the ByteByffer”. Take the example from the previ...
bytes in Java are signed, contrary to what one typically expects. What is easy to miss though, is the fact that this affects ByteBuffer.compareTo()as well. The Java API documentation for that method reads: “Two byte buffers are compared by comparing their sequences of remaining elements lexicographically, without regard to the starting position of ...
Generally, don’t use array() casually. In order for it to be used correctly you either have to know for a fact that the byte buffer is array backed, or you have to test it with hasArray() and have two separate code paths for either case. Additionally, when you use it, you must use arrayOffset()in order to determine what the zeroth position of the B...
- Peter Schuller
Methods for compacting, duplicating, and slicing a byte buffer. Byte buffers can be created either by allocation, which allocates space for the buffer's content, or by wrapping an existing byte array into a buffer. Direct vs. non-direct buffers . A byte buffer is either direct or non-direct. Given a direct byte buffer, the Java virtual machine ...
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get. Then you use ByteBuffer. get to fetch the bytes out of the buffer. Similarly there nothing in the least automatic about writing a file with a ByteBuffer. Here is the barebones code to write to a file using a ByteBuffer and FileChannel. If you run it and look at the log it produces, that should help you to get an understanding of how position,
