2025年8月4日
Java 中的 SeekableByteChannel (Java SE 24 & JDK 24) 及其示例。
您将找到大多数 SeekableByteChannel 方法的代码示例。
注解 :
- 本文可能使用了翻译软件以方便阅读。 另请查看英文原文。
简介
维护当前位置并允许改变位置的字节通道。 (机器翻译)
final var path = Path.of("R:", "java-work", "test.data");
System.out.println(path); // R:\java-work\test.data
final byte[] bytes = {10, 20, 30, 40, 50};
Files.write(path, bytes);
try (final SeekableByteChannel channel =
Files.newByteChannel(path, StandardOpenOption.READ)) {
channel.position(2);
{
System.out.println(channel.position()); // 2
final var buffer = ByteBuffer.allocate(3);
final var ret = channel.read(buffer);
System.out.println(ret); // 3
System.out.println(channel.position()); // 5
if (buffer.hasArray()) {
// [30, 40, 50]
System.out.println(Arrays.toString(buffer.array()));
}
}
channel.position(0);
{
System.out.println(channel.position()); // 0
final var buffer = ByteBuffer.allocate(5);
final var ret = channel.read(buffer);
System.out.println(ret); // 5
System.out.println(channel.position()); // 5
if (buffer.hasArray()) {
// [10, 20, 30, 40, 50]
System.out.println(Arrays.toString(buffer.array()));
}
}
}
Methods
long position ()
返回此频道的位置。 (机器翻译)
final var path = Path.of("R:", "java-work", "test.data");
System.out.println(path); // R:\java-work\test.data
final byte[] bytes = {10, 20, 30, 40, 50};
Files.write(path, bytes);
try (final SeekableByteChannel channel =
Files.newByteChannel(path, StandardOpenOption.READ)) {
final var ret1 = channel.position(2);
System.out.println(channel.equals(ret1)); // true
{
System.out.println(channel.position()); // 2
final var buffer = ByteBuffer.allocate(3);
final var ret = channel.read(buffer);
System.out.println(ret); // 3
System.out.println(channel.position()); // 5
if (buffer.hasArray()) {
// [30, 40, 50]
System.out.println(Arrays.toString(buffer.array()));
}
}
final var ret2 = channel.position(0);
System.out.println(channel.equals(ret2)); // true
{
System.out.println(channel.position()); // 0
final var buffer = ByteBuffer.allocate(5);
final var ret = channel.read(buffer);
System.out.println(ret); // 5
System.out.println(channel.position()); // 5
if (buffer.hasArray()) {
// [10, 20, 30, 40, 50]
System.out.println(Arrays.toString(buffer.array()));
}
}
}
SeekableByteChannel position (long newPosition)
设置该频道的位置。 (机器翻译)
final var path = Path.of("R:", "java-work", "test.data");
System.out.println(path); // R:\java-work\test.data
final byte[] bytes = {10, 20, 30, 40, 50};
Files.write(path, bytes);
try (final SeekableByteChannel channel =
Files.newByteChannel(path, StandardOpenOption.READ)) {
final var ret1 = channel.position(2);
System.out.println(channel.equals(ret1)); // true
{
System.out.println(channel.position()); // 2
final var buffer = ByteBuffer.allocate(3);
final var ret = channel.read(buffer);
System.out.println(ret); // 3
System.out.println(channel.position()); // 5
if (buffer.hasArray()) {
// [30, 40, 50]
System.out.println(Arrays.toString(buffer.array()));
}
}
final var ret2 = channel.position(0);
System.out.println(channel.equals(ret2)); // true
{
System.out.println(channel.position()); // 0
final var buffer = ByteBuffer.allocate(5);
final var ret = channel.read(buffer);
System.out.println(ret); // 5
System.out.println(channel.position()); // 5
if (buffer.hasArray()) {
// [10, 20, 30, 40, 50]
System.out.println(Arrays.toString(buffer.array()));
}
}
}
int read (ByteBuffer dst)
将字节序列从该通道读取到给定的缓冲区。 (机器翻译)
final var path = Path.of("R:", "java-work", "test.data");
System.out.println(path); // R:\java-work\test.data
final byte[] bytes = {10, 20, 30};
Files.write(path, bytes);
try (final SeekableByteChannel channel =
Files.newByteChannel(path, StandardOpenOption.READ)) {
final var array = new byte[5];
final var dst = ByteBuffer.wrap(array);
System.out.println(dst); // java.nio.HeapByteBuffer[pos=0 lim=5 cap=5]
System.out.println(Arrays.toString(array)); // [0, 0, 0, 0, 0]
System.out.println(channel.position()); // 0
final var ret = channel.read(dst);
System.out.println(ret); // 3
System.out.println(channel.position()); // 3
System.out.println(dst); // java.nio.HeapByteBuffer[pos=3 lim=5 cap=5]
System.out.println(Arrays.toString(array)); // [10, 20, 30, 0, 0]
}
long size ()
返回此通道所连接的实体的当前大小。 (机器翻译)
final var path = Path.of("R:", "java-work", "test.data");
System.out.println(path); // R:\java-work\test.data
final byte[] bytes = {10, 20, 30, 40, 50};
Files.write(path, bytes);
try (final SeekableByteChannel channel =
Files.newByteChannel(path, StandardOpenOption.READ)) {
final var size = channel.size();
System.out.println(size); // 5
final var dst = ByteBuffer.allocate(Math.toIntExact(size));
System.out.println(channel.read(dst)); // 5
if (dst.hasArray()) {
// [10, 20, 30, 40, 50]
System.out.println(Arrays.toString(dst.array()));
}
}
SeekableByteChannel truncate (long size)
将此通道所连接的实体截断为给定的大小。 (机器翻译)
final var path = Path.of("R:", "java-work", "test.data");
System.out.println(path); // R:\java-work\test.data
final byte[] bytes = {10, 20, 30, 40, 50};
Files.write(path, bytes);
try (final SeekableByteChannel channel =
Files.newByteChannel(path, StandardOpenOption.WRITE)) {
final var ret = channel.truncate(3);
System.out.println(channel.equals(ret)); // true
final var size = channel.size();
System.out.println(size); // 3
}
// [10, 20, 30]
System.out.println(Arrays.toString(Files.readAllBytes(path)));
int write (ByteBuffer src)
从给定的缓冲区将字节序列写入该通道。 (机器翻译)
final var path = Path.of("R:", "java-work", "test.data");
System.out.println(path); // R:\java-work\test.data
try (final SeekableByteChannel channel = Files.newByteChannel(path,
StandardOpenOption.CREATE, StandardOpenOption.WRITE)) {
final byte[] array = {10, 20, 30, 40, 50};
final var src = ByteBuffer.wrap(array);
src.limit(3);
System.out.println(src); // java.nio.HeapByteBuffer[pos=0 lim=3 cap=5]
System.out.println(channel.position()); // 0
final var ret = channel.write(src);
System.out.println(ret); // 3
System.out.println(src); // java.nio.HeapByteBuffer[pos=3 lim=3 cap=5]
System.out.println(channel.position()); // 3
}
final var bytes = Files.readAllBytes(path);
System.out.println(Arrays.toString(bytes)); // [10, 20, 30]