ByteBuffer (Java 2 Platform SE v1.4.1) - JDK 5 Documentation v1.4.1, Java 2 SDK 英文文档

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java.nio
Class ByteBuffer

java.lang.Object
  |
  +--java.nio.Buffer
        |
        +--java.nio.ByteBuffer

All Implemented Interfaces:: Comparable

Direct Known Subclasses:: MappedByteBuffer

public abstract class ByteBuffer
extends Buffer
implements Comparable

A byte buffer.

This class defines six categories of operations upon byte buffers:

Absolute and relative get and put methods that read and write single bytes;
Relative bulk get methods that transfer contiguous sequences of bytes from this buffer into an array;
Relative bulk put methods that transfer contiguous sequences of bytes from a byte array or some other byte buffer into this buffer;
Absolute and relative get and put methods that read and write values of other primitive types, translating them to and from sequences of bytes in a particular byte order;
Methods for creating view buffers, which allow a byte buffer to be viewed as a buffer containing values of some other primitive type; and
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 will make a best effort to perform native I/O operations directly upon it. That is, it will attempt to avoid copying the buffer's content to (or from) an intermediate buffer before (or after) each invocation of one of the underlying operating system's native I/O operations.

A direct byte buffer may be created by invoking the allocateDirect factory method of this class. The buffers returned by this method typically have somewhat higher allocation and deallocation costs than non-direct buffers. The contents of direct buffers may reside outside of the normal garbage-collected heap, and so their impact upon the memory footprint of an application might not be obvious. It is therefore recommended that direct buffers be allocated primarily for large, long-lived buffers that are subject to the underlying system's native I/O operations. In general it is best to allocate direct buffers only when they yield a measureable gain in program performance.

A direct byte buffer may also be created by mapping a region of a file directly into memory. An implementation of the Java platform may optionally support the creation of direct byte buffers from native code via JNI. If an instance of one of these kinds of buffers refers to an inaccessible region of memory then an attempt to access that region will not change the buffer's content and will cause an unspecified exception to be thrown either at the time of the access or at some later time.

Whether a byte buffer is direct or non-direct may be determined by invoking its isDirect method. This method is provided so that explicit buffer management can be done in performance-critical code.

Access to binary data

This class defines methods for reading and writing values of all other primitive types, except boolean. Primitive values are translated to (or from) sequences of bytes according to the buffer's current byte order, which may be retrieved and modified via the order methods. Specific byte orders are represented by instances of the ByteOrder class. The initial order of a byte buffer is always BIG_ENDIAN.

For access to heterogenous binary data, that is, sequences of values of different types, this class defines a family of absolute and relative get and put methods for each type. For 32-bit floating-point values, for example, this class defines:

 float  getFloat()
 float  getFloat(int index)
  void  putFloat(float f)
  void  putFloat(int index, float f)

Corresponding methods are defined for the types char, short, int, long, and double. The index parameters of the absolute get and put methods are in terms of bytes rather than of the type being read or written.

For access to homogeneous binary data, that is, sequences of values of the same type, this class defines methods that can create views of a given byte buffer. A view buffer is simply another buffer whose content is backed by the byte buffer. Changes to the byte buffer's content will be visible in the view buffer, and vice versa; the two buffers' position, limit, and mark values are independent. The asFloatBuffer method, for example, creates an instance of the FloatBuffer class that is backed by the byte buffer upon which the method is invoked. Corresponding view-creation methods are defined for the types char, short, int, long, and double.

View buffers have three important advantages over the families of type-specific get and put methods described above:

A view buffer is indexed not in terms of bytes but rather in terms of the type-specific size of its values;
A view buffer provides relative bulk get and put methods that can transfer contiguous sequences of values between a buffer and an array or some other buffer of the same type; and
A view buffer is potentially much more efficient because it will be direct if, and only if, its backing byte buffer is direct.

The byte order of a view buffer is fixed to be that of its byte buffer at the time that the view is created.

Invocation chaining

Methods in this class that do not otherwise have a value to return are specified to return the buffer upon which they are invoked. This allows method invocations to be chained. The sequence of statements

 bb.putInt(0xCAFEBABE);
 bb.putShort(3);
 bb.putShort(45);

can, for example, be replaced by the single statement

 bb.putInt(0xCAFEBABE).putShort(3).putShort(45);

Since:: 1.4

Method Summary

static ByteBuffer allocate(int capacity)
          Allocates a new byte buffer.

static ByteBuffer allocateDirect(int capacity)
          Allocates a new direct byte buffer.

byte[] array()
          Returns the byte array that backs this buffer  (optional operation).

int arrayOffset()
          Returns the offset within this buffer's backing array of the first element of the buffer  (optional operation).

abstract CharBuffer asCharBuffer()
          Creates a view of this byte buffer as a char buffer.

abstract DoubleBuffer asDoubleBuffer()
          Creates a view of this byte buffer as a double buffer.

abstract FloatBuffer asFloatBuffer()
          Creates a view of this byte buffer as a float buffer.

abstract IntBuffer asIntBuffer()
          Creates a view of this byte buffer as an int buffer.

abstract LongBuffer asLongBuffer()
          Creates a view of this byte buffer as a long buffer.

abstract ByteBuffer asReadOnlyBuffer()
          Creates a new, read-only byte buffer that shares this buffer's content.

abstract ShortBuffer asShortBuffer()
          Creates a view of this byte buffer as a short buffer.

abstract ByteBuffer compact()
          Compacts this buffer  (optional operation).

int compareTo(Object ob)
          Compares this buffer to another object.

abstract ByteBuffer duplicate()
          Creates a new byte buffer that shares this buffer's content.

boolean equals(Object ob)
          Tells whether or not this buffer is equal to another object.

abstract byte get()
          Relative get method.

ByteBuffer get(byte[] dst)
          Relative bulk get method.

ByteBuffer get(byte[] dst, int offset, int length)
          Relative bulk get method.

abstract byte get(int index)
          Absolute get method.

abstract char getChar()
          Relative get method for reading a char value.

abstract char getChar(int index)
          Absolute get method for reading a char value.

abstract double getDouble()
          Relative get method for reading a double value.

abstract double getDouble(int index)
          Absolute get method for reading a double value.

abstract float getFloat()
          Relative get method for reading a float value.

abstract float getFloat(int index)
          Absolute get method for reading a float value.

abstract int getInt()
          Relative get method for reading an int value.

abstract int getInt(int index)
          Absolute get method for reading an int value.

abstract long getLong()
          Relative get method for reading a long value.

abstract long getLong(int index)
          Absolute get method for reading a long value.

abstract short getShort()
          Relative get method for reading a short value.

abstract short getShort(int index)
          Absolute get method for reading a short value.

boolean hasArray()
          Tells whether or not this buffer is backed by an accessible byte array.

int hashCode()
          Returns the current hash code of this buffer.

abstract boolean isDirect()
          Tells whether or not this byte buffer is direct.

ByteOrder order()
          Retrieves this buffer's byte order.

ByteBuffer order(ByteOrder bo)
          Modifies this buffer's byte order.

abstract ByteBuffer put(byte b)
          Relative put method  (optional operation).

ByteBuffer put(byte[] src)
          Relative bulk put method  (optional operation).

ByteBuffer put(byte[] src, int offset, int length)
          Relative bulk put method  (optional operation).

ByteBuffer put(ByteBuffer src)
          Relative bulk put method  (optional operation).

abstract ByteBuffer put(int index, byte b)
          Absolute put method  (optional operation).

abstract ByteBuffer putChar(char value)
          Relative put method for writing a char value  (optional operation).

abstract ByteBuffer putChar(int index, char value)
          Absolute put method for writing a char value  (optional operation).

abstract ByteBuffer putDouble(double value)
          Relative put method for writing a double value  (optional operation).

abstract ByteBuffer putDouble(int index, double value)
          Absolute put method for writing a double value  (optional operation).

abstract ByteBuffer putFloat(float value)
          Relative put method for writing a float value  (optional operation).

abstract ByteBuffer putFloat(int index, float value)
          Absolute put method for writing a float value  (optional operation).

abstract ByteBuffer putInt(int value)
          Relative put method for writing an int value  (optional operation).

abstract ByteBuffer putInt(int index, int value)
          Absolute put method for writing an int value  (optional operation).

abstract ByteBuffer putLong(int index, long value)
          Absolute put method for writing a long value  (optional operation).

abstract ByteBuffer putLong(long value)
          Relative put method for writing a long value  (optional operation).

abstract ByteBuffer putShort(int index, short value)
          Absolute put method for writing a short value  (optional operation).

abstract ByteBuffer putShort(short value)
          Relative put method for writing a short value  (optional operation).

abstract ByteBuffer slice()
          Creates a new byte buffer whose content is a shared subsequence of this buffer's content.

String toString()
          Returns a string summarizing the state of this buffer.

static ByteBuffer wrap(byte[] array)
          Wraps a byte array into a buffer.

static ByteBuffer wrap(byte[] array, int offset, int length)
          Wraps a byte array into a buffer.

Methods inherited from class java.nio.Buffer

capacity, clear, flip, hasRemaining, isReadOnly, limit, limit, mark, position, position, remaining, reset, rewind

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Method Detail

allocateDirect

public static ByteBuffer allocateDirect(int capacity)

Allocates a new direct byte buffer.

The new buffer's position will be zero, its limit will be its capacity, and its mark will be undefined. Whether or not it has a backing array is unspecified.

Parameters:: capacity - The new buffer's capacity, in bytes
Returns:: The new byte buffer

allocate

public static ByteBuffer allocate(int capacity)

Allocates a new byte buffer.

The new buffer's position will be zero, its limit will be its capacity, and its mark will be undefined. It will have a backing array, and its array offset will be zero.

Parameters:: capacity - The new buffer's capacity, in bytes
Returns:: The new byte buffer

wrap

public static ByteBuffer wrap(byte[] array,
                              int offset,
                              int length)

Wraps a byte array into a buffer.

The new buffer will be backed by the the given byte array; that is, modifications to the buffer will cause the array to be modified and vice versa. The new buffer's capacity will be array.length, its position will be offset, its limit will be offset + length, and its mark will be undefined. Its backing array will be the given array, and its array offset will be zero.

Parameters:: array - The array that will back the new buffer; offset - The offset of the subarray to be used; must be non-negative and no larger than array.length. The new buffer's position will be set to this value.; length - The length of the subarray to be used; must be non-negative and no larger than array.length - offset. The new buffer's limit will be set to offset + length.
Returns:: The new byte buffer
Throws:: IndexOutOfBoundsException - If the preconditions on the offset and length parameters do not hold

wrap

public static ByteBuffer wrap(byte[] array)

Wraps a byte array into a buffer.

The new buffer will be backed by the the given byte array; that is, modifications to the buffer will cause the array to be modified and vice versa. The new buffer's capacity and limit will be array.length, its position will be zero, and its mark will be undefined. Its backing array will be the given array, and its array offset will be zero.

Parameters:: array - The array that will back this buffer
Returns:: The new byte buffer

slice

public abstract ByteBuffer slice()

Creates a new byte buffer whose content is a shared subsequence of this buffer's content.

The content of the new buffer will start at this buffer's current position. Changes to this buffer's content will be visible in the new buffer, and vice versa; the two buffers' position, limit, and mark values will be independent.

The new buffer's position will be zero, its capacity and its limit will be the number of bytes remaining in this buffer, and its mark will be undefined. The new buffer will be direct if, and only if, this buffer is direct, and it will be read-only if, and only if, this buffer is read-only.

Returns:: The new byte buffer

duplicate

public abstract ByteBuffer duplicate()

Creates a new byte buffer that shares this buffer's content.

The content of the new buffer will be that of this buffer. Changes to this buffer's content will be visible in the new buffer, and vice versa; the two buffers' position, limit, and mark values will be independent.

The new buffer's capacity, limit, position, and mark values will be identical to those of this buffer. The new buffer will be direct if, and only if, this buffer is direct, and it will be read-only if, and only if, this buffer is read-only.

Returns:: The new byte buffer

asReadOnlyBuffer

public abstract ByteBuffer asReadOnlyBuffer()

Creates a new, read-only byte buffer that shares this buffer's content.

The content of the new buffer will be that of this buffer. Changes to this buffer's content will be visible in the new buffer; the new buffer itself, however, will be read-only and will not allow the shared content to be modified. The two buffers' position, limit, and mark values will be independent.

The new buffer's capacity, limit, position, and mark values will be identical to those of this buffer.

If this buffer is itself read-only then this method behaves in exactly the same way as the duplicate method.

Returns:: The new, read-only byte buffer

get

public abstract byte get()

Relative get method. Reads the byte at this buffer's current position, and then increments the position.

Returns:: The byte at the buffer's current position
Throws:: BufferUnderflowException - If the buffer's current position is not smaller than its limit

put

public abstract ByteBuffer put(byte b)

Relative put method (optional operation).

Writes the given byte into this buffer at the current position, and then increments the position.

Parameters:: b - The byte to be written
Returns:: This buffer
Throws:: BufferOverflowException - If this buffer's current position is not smaller than its limit; ReadOnlyBufferException - If this buffer is read-only

get

public abstract byte get(int index)

Absolute get method. Reads the byte at the given index.

Parameters:: index - The index from which the byte will be read
Returns:: The byte at the given index
Throws:: IndexOutOfBoundsException - If index is negative or not smaller than the buffer's limit

put

public abstract ByteBuffer put(int index,
                               byte b)

Absolute put method (optional operation).

Writes the given byte into this buffer at the given index.

Parameters:: index - The index at which the byte will be written; b - The byte value to be written
Returns:: This buffer
Throws:: IndexOutOfBoundsException - If index is negative or not smaller than the buffer's limit; ReadOnlyBufferException - If this buffer is read-only

get

public ByteBuffer get(byte[] dst,
                      int offset,
                      int length)

Relative bulk get method.

This method transfers bytes from this buffer into the given destination array. If there are fewer bytes remaining in the buffer than are required to satisfy the request, that is, if length > remaining(), then no bytes are transferred and a BufferUnderflowException is thrown.

Otherwise, this method copies length bytes from this buffer into the given array, starting at the current position of this buffer and at the given offset in the array. The position of this buffer is then incremented by length.

In other words, an invocation of this method of the form src.get(dst, off, len) has exactly the same effect as the loop

     for (int i = off; i < off + len; i++)
         dst[i] = src.get();

except that it first checks that there are sufficient bytes in this buffer and it is potentially much more efficient.

Parameters:: dst - The array into which bytes are to be written; offset - The offset within the array of the first byte to be written; must be non-negative and no larger than dst.length; length - The maximum number of bytes to be written to the given array; must be non-negative and no larger than dst.length - offset
Returns:: This buffer
Throws:: BufferUnderflowException - If there are fewer than length bytes remaining in this buffer; IndexOutOfBoundsException - If the preconditions on the offset and length parameters do not hold

get

public ByteBuffer get(byte[] dst)

Relative bulk get method.

This method transfers bytes from this buffer into the given destination array. An invocation of this method of the form src.get(a) behaves in exactly the same way as the invocation

     src.get(a, 0, a.length)

Returns:: This buffer
Throws:: BufferUnderflowException - If there are fewer than length bytes remaining in this buffer

put

public ByteBuffer put(ByteBuffer src)

Relative bulk put method (optional operation).

This method transfers the bytes remaining in the given source buffer into this buffer. If there are more bytes remaining in the source buffer than in this buffer, that is, if src.remaining() > remaining(), then no bytes are transferred and a BufferOverflowException is thrown.

Otherwise, this method copies n = src.remaining() bytes from the given buffer into this buffer, starting at each buffer's current position. The positions of both buffers are then incremented by n.

In other words, an invocation of this method of the form dst.put(src) has exactly the same effect as the loop

     while (src.hasRemaining())
         dst.put(src.get());

except that it first checks that there is sufficient space in this buffer and it is potentially much more efficient.

Parameters:: src - The source buffer from which bytes are to be read; must not be this buffer
Returns:: This buffer
Throws:: BufferOverflowException - If there is insufficient space in this buffer for the remaining bytes in the source buffer; IllegalArgumentException - If the source buffer is this buffer; ReadOnlyBufferException - If this buffer is read-only

put

public ByteBuffer put(byte[] src,
                      int offset,
                      int length)

Relative bulk put method (optional operation).

This method transfers bytes into this buffer from the given source array. If there are more bytes to be copied from the array than remain in this buffer, that is, if length > remaining(), then no bytes are transferred and a BufferOverflowException is thrown.

Otherwise, this method copies length bytes from the given array into this buffer, starting at the given offset in the array and at the current position of this buffer. The position of this buffer is then incremented by length.

In other words, an invocation of this method of the form dst.put(src, off, len) has exactly the same effect as the loop

     for (int i = off; i < off + len; i++)
         dst.put(a[i]);

except that it first checks that there is sufficient space in this buffer and it is potentially much more efficient.

Parameters:: offset - The offset within the array of the first byte to be read; must be non-negative and no larger than array.length; length - The number of bytes to be read from the given array; must be non-negative and no larger than array.length - offset
Returns:: This buffer
Throws:: BufferOverflowException - If there is insufficient space in this buffer; IndexOutOfBoundsException - If the preconditions on the offset and length parameters do not hold; ReadOnlyBufferException - If this buffer is read-only

put

public final ByteBuffer put(byte[] src)

Relative bulk put method (optional operation).

This method transfers the entire content of the given source byte array into this buffer. An invocation of this method of the form dst.put(a) behaves in exactly the same way as the invocation

     dst.put(a, 0, a.length)

Returns:: This buffer
Throws:: BufferOverflowException - If there is insufficient space in this buffer; ReadOnlyBufferException - If this buffer is read-only

hasArray

public final boolean hasArray()

Tells whether or not this buffer is backed by an accessible byte array.

If this method returns true then the array and arrayOffset methods may safely be invoked.

Returns:: true if, and only if, this buffer is backed by an array and is not read-only

array

public final byte[] array()

Returns the byte array that backs this buffer (optional operation).

Modifications to this buffer's content will cause the returned array's content to be modified, and vice versa.

Invoke the hasArray method before invoking this method in order to ensure that this buffer has an accessible backing array.

Returns:: The array that backs this buffer
Throws:: ReadOnlyBufferException - If this buffer is backed by an array but is read-only; UnsupportedOperationException - If this buffer is not backed by an accessible array

arrayOffset

public final int arrayOffset()

Returns the offset within this buffer's backing array of the first element of the buffer (optional operation).

If this buffer is backed by an array then buffer position p corresponds to array index p + arrayOffset().

Invoke the hasArray method before invoking this method in order to ensure that this buffer has an accessible backing array.

Returns:: The offset within this buffer's array of the first element of the buffer
Throws:: ReadOnlyBufferException - If this buffer is backed by an array but is read-only; UnsupportedOperationException - If this buffer is not backed by an accessible array

compact

public abstract ByteBuffer compact()

Compacts this buffer (optional operation).

The bytes between the buffer's current position and its limit, if any, are copied to the beginning of the buffer. That is, the byte at index p = position() is copied to index zero, the byte at index p + 1 is copied to index one, and so forth until the byte at index limit() - 1 is copied to index n = limit() - 1 - p. The buffer's position is then set to n+1 and its limit is set to its capacity. The mark, if defined, is discarded.

The buffer's position is set to the number of bytes copied, rather than to zero, so that an invocation of this method can be followed immediately by an invocation of another relative put method.

Invoke this method after writing data from a buffer in case the write was incomplete. The following loop, for example, copies bytes from one channel to another via the buffer buf:

 buf.clear();          // Prepare buffer for use
 for (;;) {
     if (in.read(buf) < 0 && !buf.hasRemaining())
         break;        // No more bytes to transfer
     buf.flip();
     out.write(buf);
     buf.compact();    // In case of partial write
 }

Returns:: This buffer
Throws:: ReadOnlyBufferException - If this buffer is read-only

isDirect

public abstract boolean isDirect()

Tells whether or not this byte buffer is direct.

Returns:: true if, and only if, this buffer is direct

toString

public String toString()

Returns a string summarizing the state of this buffer.

Overrides:: toString in class Object

Returns:: A summary string

hashCode

public int hashCode()

Returns the current hash code of this buffer.

The hash code of a byte buffer depends only upon its remaining elements; that is, upon the elements from position() up to, and including, the element at limit() - 1.

Because buffer hash codes are content-dependent, it is inadvisable to use buffers as keys in hash maps or similar data structures unless it is known that their contents will not change.

Overrides:: hashCode in class Object

Returns:: The current hash code of this buffer
See Also:: Object.equals(java.lang.Object), Hashtable

equals

public boolean equals(Object ob)

Tells whether or not this buffer is equal to another object.

Two byte buffers are equal if, and only if,

They have the same element type,
They have the same number of remaining elements, and
The two sequences of remaining elements, considered independently of their starting positions, are pointwise equal.

A byte buffer is not equal to any other type of object.

Overrides:: equals in class Object

Parameters:: ob - The object to which this buffer is to be compared
Returns:: true if, and only if, this buffer is equal to the given object
See Also:: Object.hashCode(), Hashtable

compareTo

public int compareTo(Object ob)

Compares this buffer to another object.

Two byte buffers are compared by comparing their sequences of remaining elements lexicographically, without regard to the starting position of each sequence within its corresponding buffer.

A byte buffer is not comparable to any other type of object.

Specified by:: compareTo in interface Comparable

Parameters:: ob - the Object to be compared.
Returns:: A negative integer, zero, or a positive integer as this buffer is less than, equal to, or greater than the given buffer
Throws:: ClassCastException - If the argument is not a byte buffer

order

public final ByteOrder order()

Retrieves this buffer's byte order.

The byte order is used when reading or writing multibyte values, and when creating buffers that are views of this byte buffer. The order of a newly-created byte buffer is always BIG_ENDIAN.

Returns:: This buffer's byte order

order

public final ByteBuffer order(ByteOrder bo)

Modifies this buffer's byte order.

Parameters:: bo - The new byte order, either BIG_ENDIAN or LITTLE_ENDIAN
Returns:: This buffer

getChar

public abstract char getChar()

Relative get method for reading a char value.

Reads the next two bytes at this buffer's current position, composing them into a char value according to the current byte order, and then increments the position by two.

Returns:: The char value at the buffer's current position
Throws:: BufferUnderflowException - If there are fewer than two bytes remaining in this buffer

putChar

public abstract ByteBuffer putChar(char value)

Relative put method for writing a char value (optional operation).

Writes two bytes containing the given char value, in the current byte order, into this buffer at the current position, and then increments the position by two.

Parameters:: value - The char value to be written
Returns:: This buffer
Throws:: BufferOverflowException - If there are fewer than two bytes remaining in this buffer

getChar

public abstract char getChar(int index)

Absolute get method for reading a char value.

Reads two bytes at the given index, composing them into a char value according to the current byte order.

Parameters:: index - The index from which the bytes will be read
Returns:: The char value at the given index
Throws:: IndexOutOfBoundsException - If index is negative or not smaller than the buffer's limit, minus one

putChar

public abstract ByteBuffer putChar(int index,
                                   char value)

Absolute put method for writing a char value (optional operation).

Writes two bytes containing the given char value, in the current byte order, into this buffer at the given index.

Parameters:: index - The index at which the bytes will be written; value - The char value to be written
Returns:: This buffer
Throws:: IndexOutOfBoundsException - If index is negative or not smaller than the buffer's limit, minus one

asCharBuffer

public abstract CharBuffer asCharBuffer()

Creates a view of this byte buffer as a char buffer.

The new buffer's position will be zero, its capacity and its limit will be the number of bytes remaining in this buffer divided by two, and its mark will be undefined. The new buffer will be direct if, and only if, this buffer is direct, and it will be read-only if, and only if, this buffer is read-only.

Returns:: A new char buffer

getShort

public abstract short getShort()

Relative get method for reading a short value.

Reads the next two bytes at this buffer's current position, composing them into a short value according to the current byte order, and then increments the position by two.

Returns:: The short value at the buffer's current position
Throws:: BufferUnderflowException - If there are fewer than two bytes remaining in this buffer

putShort

public abstract ByteBuffer putShort(short value)

Relative put method for writing a short value (optional operation).

Writes two bytes containing the given short value, in the current byte order, into this buffer at the current position, and then increments the position by two.

Parameters:: value - The short value to be written
Returns:: This buffer
Throws:: BufferOverflowException - If there are fewer than two bytes remaining in this buffer

getShort

public abstract short getShort(int index)

Absolute get method for reading a short value.

Reads two bytes at the given index, composing them into a short value according to the current byte order.

Parameters:: index - The index from which the bytes will be read
Returns:: The short value at the given index
Throws:: IndexOutOfBoundsException - If index is negative or not smaller than the buffer's limit, minus one

putShort

public abstract ByteBuffer putShort(int index,
                                    short value)

Absolute put method for writing a short value (optional operation).

Writes two bytes containing the given short value, in the current byte order, into this buffer at the given index.

Parameters:: index - The index at which the bytes will be written; value - The short value to be written
Returns:: This buffer
Throws:: IndexOutOfBoundsException - If index is negative or not smaller than the buffer's limit, minus one

asShortBuffer

public abstract ShortBuffer asShortBuffer()

Creates a view of this byte buffer as a short buffer.

Returns:: A new short buffer

getInt

public abstract int getInt()

Relative get method for reading an int value.

Reads the next four bytes at this buffer's current position, composing them into an int value according to the current byte order, and then increments the position by four.

Returns:: The int value at the buffer's current position
Throws:: BufferUnderflowException - If there are fewer than four bytes remaining in this buffer

putInt

public abstract ByteBuffer putInt(int value)

Relative put method for writing an int value (optional operation).

Writes four bytes containing the given int value, in the current byte order, into this buffer at the current position, and then increments the position by four.

Parameters:: value - The int value to be written
Returns:: This buffer
Throws:: BufferOverflowException - If there are fewer than four bytes remaining in this buffer

getInt

public abstract int getInt(int index)

Absolute get method for reading an int value.

Reads four bytes at the given index, composing them into a int value according to the current byte order.

Parameters:: index - The index from which the bytes will be read
Returns:: The int value at the given index
Throws:: IndexOutOfBoundsException - If index is negative or not smaller than the buffer's limit, minus three

putInt

public abstract ByteBuffer putInt(int index,
                                  int value)

Absolute put method for writing an int value (optional operation).

Writes four bytes containing the given int value, in the current byte order, into this buffer at the given index.

Parameters:: index - The index at which the bytes will be written; value - The int value to be written
Returns:: This buffer
Throws:: IndexOutOfBoundsException - If index is negative or not smaller than the buffer's limit, minus three

asIntBuffer

public abstract IntBuffer asIntBuffer()

Creates a view of this byte buffer as an int buffer.

The new buffer's position will be zero, its capacity and its limit will be the number of bytes remaining in this buffer divided by four, and its mark will be undefined. The new buffer will be direct if, and only if, this buffer is direct, and it will be read-only if, and only if, this buffer is read-only.

Returns:: A new int buffer

getLong

public abstract long getLong()

Relative get method for reading a long value.

Reads the next eight bytes at this buffer's current position, composing them into a long value according to the current byte order, and then increments the position by eight.

Returns:: The long value at the buffer's current position
Throws:: BufferUnderflowException - If there are fewer than eight bytes remaining in this buffer

putLong

public abstract ByteBuffer putLong(long value)

Relative put method for writing a long value (optional operation).

Writes eight bytes containing the given long value, in the current byte order, into this buffer at the current position, and then increments the position by eight.

Parameters:: value - The long value to be written
Returns:: This buffer
Throws:: BufferOverflowException - If there are fewer than eight bytes remaining in this buffer

getLong

public abstract long getLong(int index)

Absolute get method for reading a long value.

Reads eight bytes at the given index, composing them into a long value according to the current byte order.

Parameters:: index - The index from which the bytes will be read
Returns:: The long value at the given index
Throws:: IndexOutOfBoundsException - If index is negative or not smaller than the buffer's limit, minus seven

putLong

public abstract ByteBuffer putLong(int index,
                                   long value)

Absolute put method for writing a long value (optional operation).

Writes eight bytes containing the given long value, in the current byte order, into this buffer at the given index.

Parameters:: index - The index at which the bytes will be written; value - The long value to be written
Returns:: This buffer
Throws:: IndexOutOfBoundsException - If index is negative or not smaller than the buffer's limit, minus seven

asLongBuffer

public abstract LongBuffer asLongBuffer()

Creates a view of this byte buffer as a long buffer.

The new buffer's position will be zero, its capacity and its limit will be the number of bytes remaining in this buffer divided by eight, and its mark will be undefined. The new buffer will be direct if, and only if, this buffer is direct, and it will be read-only if, and only if, this buffer is read-only.

Returns:: A new long buffer

getFloat

public abstract float getFloat()

Relative get method for reading a float value.

Reads the next four bytes at this buffer's current position, composing them into a float value according to the current byte order, and then increments the position by four.

Returns:: The float value at the buffer's current position
Throws:: BufferUnderflowException - If there are fewer than four bytes remaining in this buffer

putFloat

public abstract ByteBuffer putFloat(float value)

Relative put method for writing a float value (optional operation).

Writes four bytes containing the given float value, in the current byte order, into this buffer at the current position, and then increments the position by four.

Parameters:: value - The float value to be written
Returns:: This buffer
Throws:: BufferOverflowException - If there are fewer than four bytes remaining in this buffer

getFloat

public abstract float getFloat(int index)

Absolute get method for reading a float value.

Reads four bytes at the given index, composing them into a float value according to the current byte order.

Parameters:: index - The index from which the bytes will be read
Returns:: The float value at the given index
Throws:: IndexOutOfBoundsException - If index is negative or not smaller than the buffer's limit, minus three

putFloat

public abstract ByteBuffer putFloat(int index,
                                    float value)

Absolute put method for writing a float value (optional operation).

Writes four bytes containing the given float value, in the current byte order, into this buffer at the given index.

Parameters:: index - The index at which the bytes will be written; value - The float value to be written
Returns:: This buffer
Throws:: IndexOutOfBoundsException - If index is negative or not smaller than the buffer's limit, minus three

asFloatBuffer

public abstract FloatBuffer asFloatBuffer()

Creates a view of this byte buffer as a float buffer.

Returns:: A new float buffer

getDouble

public abstract double getDouble()

Relative get method for reading a double value.

Reads the next eight bytes at this buffer's current position, composing them into a double value according to the current byte order, and then increments the position by eight.

Returns:: The double value at the buffer's current position
Throws:: BufferUnderflowException - If there are fewer than eight bytes remaining in this buffer

putDouble

public abstract ByteBuffer putDouble(double value)

Relative put method for writing a double value (optional operation).

Writes eight bytes containing the given double value, in the current byte order, into this buffer at the current position, and then increments the position by eight.

Parameters:: value - The double value to be written
Returns:: This buffer
Throws:: BufferOverflowException - If there are fewer than eight bytes remaining in this buffer

getDouble

public abstract double getDouble(int index)

Absolute get method for reading a double value.

Reads eight bytes at the given index, composing them into a double value according to the current byte order.

Parameters:: index - The index from which the bytes will be read
Returns:: The double value at the given index
Throws:: IndexOutOfBoundsException - If index is negative or not smaller than the buffer's limit, minus seven

putDouble

public abstract ByteBuffer putDouble(int index,
                                     double value)

Absolute put method for writing a double value (optional operation).

Writes eight bytes containing the given double value, in the current byte order, into this buffer at the given index.

Parameters:: index - The index at which the bytes will be written; value - The double value to be written
Returns:: This buffer
Throws:: IndexOutOfBoundsException - If index is negative or not smaller than the buffer's limit, minus seven

asDoubleBuffer

public abstract DoubleBuffer asDoubleBuffer()

Creates a view of this byte buffer as a double buffer.

Returns:: A new double buffer

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Method Summary
`static ByteBuffer`	`allocate(int capacity)` Allocates a new byte buffer.
`static ByteBuffer`	`allocateDirect(int capacity)` Allocates a new direct byte buffer.
`byte[]`	`array()` Returns the byte array that backs this buffer (optional operation).
`int`	`arrayOffset()` Returns the offset within this buffer's backing array of the first element of the buffer (optional operation).
`abstract CharBuffer`	`asCharBuffer()` Creates a view of this byte buffer as a char buffer.
`abstract DoubleBuffer`	`asDoubleBuffer()` Creates a view of this byte buffer as a double buffer.
`abstract FloatBuffer`	`asFloatBuffer()` Creates a view of this byte buffer as a float buffer.
`abstract IntBuffer`	`asIntBuffer()` Creates a view of this byte buffer as an int buffer.
`abstract LongBuffer`	`asLongBuffer()` Creates a view of this byte buffer as a long buffer.
`abstract ByteBuffer`	`asReadOnlyBuffer()` Creates a new, read-only byte buffer that shares this buffer's content.
`abstract ShortBuffer`	`asShortBuffer()` Creates a view of this byte buffer as a short buffer.
`abstract ByteBuffer`	`compact()` Compacts this buffer (optional operation).
`int`	`compareTo(Object ob)` Compares this buffer to another object.
`abstract ByteBuffer`	`duplicate()` Creates a new byte buffer that shares this buffer's content.
`boolean`	`equals(Object ob)` Tells whether or not this buffer is equal to another object.
`abstract byte`	`get()` Relative get method.
`ByteBuffer`	`get(byte[] dst)` Relative bulk get method.
`ByteBuffer`	`get(byte[] dst, int offset, int length)` Relative bulk get method.
`abstract byte`	`get(int index)` Absolute get method.
`abstract char`	`getChar()` Relative get method for reading a char value.
`abstract char`	`getChar(int index)` Absolute get method for reading a char value.
`abstract double`	`getDouble()` Relative get method for reading a double value.
`abstract double`	`getDouble(int index)` Absolute get method for reading a double value.
`abstract float`	`getFloat()` Relative get method for reading a float value.
`abstract float`	`getFloat(int index)` Absolute get method for reading a float value.
`abstract int`	`getInt()` Relative get method for reading an int value.
`abstract int`	`getInt(int index)` Absolute get method for reading an int value.
`abstract long`	`getLong()` Relative get method for reading a long value.
`abstract long`	`getLong(int index)` Absolute get method for reading a long value.
`abstract short`	`getShort()` Relative get method for reading a short value.
`abstract short`	`getShort(int index)` Absolute get method for reading a short value.
`boolean`	`hasArray()` Tells whether or not this buffer is backed by an accessible byte array.
`int`	`hashCode()` Returns the current hash code of this buffer.
`abstract boolean`	`isDirect()` Tells whether or not this byte buffer is direct.
`ByteOrder`	`order()` Retrieves this buffer's byte order.
`ByteBuffer`	`order(ByteOrder bo)` Modifies this buffer's byte order.
`abstract ByteBuffer`	`put(byte b)` Relative put method (optional operation).
`ByteBuffer`	`put(byte[] src)` Relative bulk put method (optional operation).
`ByteBuffer`	`put(byte[] src, int offset, int length)` Relative bulk put method (optional operation).
`ByteBuffer`	`put(ByteBuffer src)` Relative bulk put method (optional operation).
`abstract ByteBuffer`	`put(int index, byte b)` Absolute put method (optional operation).
`abstract ByteBuffer`	`putChar(char value)` Relative put method for writing a char value (optional operation).
`abstract ByteBuffer`	`putChar(int index, char value)` Absolute put method for writing a char value (optional operation).
`abstract ByteBuffer`	`putDouble(double value)` Relative put method for writing a double value (optional operation).
`abstract ByteBuffer`	`putDouble(int index, double value)` Absolute put method for writing a double value (optional operation).
`abstract ByteBuffer`	`putFloat(float value)` Relative put method for writing a float value (optional operation).
`abstract ByteBuffer`	`putFloat(int index, float value)` Absolute put method for writing a float value (optional operation).
`abstract ByteBuffer`	`putInt(int value)` Relative put method for writing an int value (optional operation).
`abstract ByteBuffer`	`putInt(int index, int value)` Absolute put method for writing an int value (optional operation).
`abstract ByteBuffer`	`putLong(int index, long value)` Absolute put method for writing a long value (optional operation).
`abstract ByteBuffer`	`putLong(long value)` Relative put method for writing a long value (optional operation).
`abstract ByteBuffer`	`putShort(int index, short value)` Absolute put method for writing a short value (optional operation).
`abstract ByteBuffer`	`putShort(short value)` Relative put method for writing a short value (optional operation).
`abstract ByteBuffer`	`slice()` Creates a new byte buffer whose content is a shared subsequence of this buffer's content.
`String`	`toString()` Returns a string summarizing the state of this buffer.
`static ByteBuffer`	`wrap(byte[] array)` Wraps a byte array into a buffer.
`static ByteBuffer`	`wrap(byte[] array, int offset, int length)` Wraps a byte array into a buffer.

ByteBuffer (Java 2 Platform SE v1.4.1) - JDK 5 Documentation v1.4.1, Java 2 SDK 英文文档

java.nio Class ByteBuffer

Direct vs. non-direct buffers

Access to binary data

Invocation chaining

allocateDirect

allocate

wrap

wrap

slice

duplicate

asReadOnlyBuffer

get

put

get

put

get

get

put

put

put

hasArray

array

arrayOffset

compact

isDirect

toString

hashCode

equals

compareTo

order

order

getChar

putChar

getChar

putChar

asCharBuffer

getShort

putShort

getShort

putShort

asShortBuffer

getInt

putInt

getInt

putInt

asIntBuffer

getLong

putLong

getLong

putLong

asLongBuffer

getFloat

putFloat

getFloat

putFloat

asFloatBuffer

getDouble

putDouble

getDouble

putDouble

asDoubleBuffer

java.nio
Class ByteBuffer