This class defines four categories of operations upon character buffers:
Absolute and relative get
and
put
methods that read and write
single characters;
Relative bulk get
methods that transfer contiguous sequences of characters from this buffer
into an array; and
Relative bulk put
methods that transfer contiguous sequences of characters from a
character array, a string, or some other character
buffer into this buffer; and
Methods for compacting
, duplicating
, and slicing
a character buffer.
Character buffers can be created either by allocation
, which allocates space for the buffer's
content, by #wrap(char[]) wrapping
an existing
character array or string into a buffer, or by creating a
view of an existing byte buffer
Like a byte buffer, a character buffer is either direct or non-direct. A character buffer created via the wrap methods of this class will be non-direct. A character buffer created as a view of a byte buffer will be direct if, and only if, the byte buffer itself is direct. Whether or not a character buffer is direct may be determined by invoking the isDirect method.
This class implements the CharSequence interface so that character buffers may be used wherever character sequences are accepted, for example in the regular-expression package java.util.regex .
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
cb.put("text/");
cb.put(subtype);
cb.put("; charset=");
cb.put(enc);
cb.put("text/").put(subtype).put("; charset=").put(enc); 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.
Depending on which class implements the character sequence csq, the entire sequence may not be appended. For instance, if csq is a java.nio.CharBuffer then the subsequence to append is defined by the buffer's position and limit.
An invocation of this method of the form out.append(csq, start, end) when csq is not null, behaves in exactly the same way as the invocation
out.append(csq.subSequence(start, end)) 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.
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.
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.
char value at the specified index. An index ranges from zero
to length() - 1. The first char value of the sequence is at
index zero, the next at index one, and so on, as for array
indexing.
If the char value specified by the index is a
surrogate, the surrogate
value is returned.
Invoke this method before using a sequence of channel-read or put operations to fill this buffer. For example:
buf.clear(); // Prepare buffer for reading in.read(buf); // Read data
This method does not actually erase the data in the buffer, but it is named as if it did because it will most often be used in situations in which that might as well be the case.
The characters between the buffer's current position and its limit, if any, are copied to the beginning of the buffer. That is, the character at index p = position() is copied to index zero, the character at index p + 1 is copied to index one, and so forth until the character 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 characters copied, rather than to zero, so that an invocation of this method can be followed immediately by an invocation of another relative put method.
Two char 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 char buffer is not comparable to any other type of object.
In the foregoing description, the notation sgn(expression) designates the mathematical signum function, which is defined to return one of -1, 0, or 1 according to whether the value of expression is negative, zero or positive. The implementor must ensure sgn(x.compareTo(y)) == -sgn(y.compareTo(x)) for all x and y. (This implies that x.compareTo(y) must throw an exception iff y.compareTo(x) throws an exception.)
The implementor must also ensure that the relation is transitive: (x.compareTo(y)>0 && y.compareTo(z)>0) implies x.compareTo(z)>0.
Finally, the implementer must ensure that x.compareTo(y)==0 implies that sgn(x.compareTo(z)) == sgn(y.compareTo(z)), for all z.
It is strongly recommended, but not strictly required that (x.compareTo(y)==0) == (x.equals(y)). Generally speaking, any class that implements the Comparable interface and violates this condition should clearly indicate this fact. The recommended language is "Note: this class has a natural ordering that is inconsistent with equals."
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.
Two char 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 char buffer is not equal to any other type of object.
After a sequence of channel-read or put operations, invoke this method to prepare for a sequence of channel-write or relative get operations. For example:
buf.put(magic); // Prepend header in.read(buf); // Read data into rest of buffer buf.flip(); // Flip buffer out.write(buf); // Write header + data to channel
This method is often used in conjunction with the compact method when transferring data from one place to another.
This method transfers characters 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) This method transfers characters from this buffer into the given destination array. If there are fewer characters remaining in the buffer than are required to satisfy the request, that is, if length > remaining(), then no characters are transferred and a BufferUnderflowException is thrown.
Otherwise, this method copies length characters 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 characters in
this buffer and it is potentially much more efficient. If this method returns true then the array and arrayOffset methods may safely be invoked.
The hash code of a char 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.
chars in the sequence.wait methods.
The awakened thread will not be able to proceed until the current thread relinquishes the lock on this object. The awakened thread will compete in the usual manner with any other threads that might be actively competing to synchronize on this object; for example, the awakened thread enjoys no reliable privilege or disadvantage in being the next thread to lock this object.
This method should only be called by a thread that is the owner of this object's monitor. A thread becomes the owner of the object's monitor in one of three ways:
synchronized statement
that synchronizes on the object.
Class, by executing a
synchronized static method of that class.
Only one thread at a time can own an object's monitor.
wait methods.
The awakened threads will not be able to proceed until the current thread relinquishes the lock on this object. The awakened threads will compete in the usual manner with any other threads that might be actively competing to synchronize on this object; for example, the awakened threads enjoy no reliable privilege or disadvantage in being the next thread to lock this object.
This method should only be called by a thread that is the owner
of this object's monitor. See the notify method for a
description of the ways in which a thread can become the owner of
a monitor.
The byte order of a character buffer created by allocation or by
wrapping an existing char array is the native order
of the underlying
hardware. The byte order of a character buffer created as a view of a byte buffer is that of the
byte buffer at the moment that the view is created.
Writes the given character into this buffer at the current position, and then increments the position.
This method transfers the entire content of the given source character 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) This method transfers characters into this buffer from the given source array. If there are more characters to be copied from the array than remain in this buffer, that is, if length > remaining(), then no characters are transferred and a BufferOverflowException is thrown.
Otherwise, this method copies length characters 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. This method transfers the characters remaining in the given source buffer into this buffer. If there are more characters remaining in the source buffer than in this buffer, that is, if src.remaining() > remaining(), then no characters are transferred and a BufferOverflowException is thrown.
Otherwise, this method copies n = src.remaining() characters 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. Writes the given character into this buffer at the given index.
This method transfers the entire content of the given source string into this buffer. An invocation of this method of the form dst.put(s) behaves in exactly the same way as the invocation
dst.put(s, 0, s.length()) This method transfers characters from the given string into this buffer. If there are more characters to be copied from the string than remain in this buffer, that is, if end - start > remaining(), then no characters are transferred and a BufferOverflowException is thrown.
Otherwise, this method copies n = end - start characters from the given string into this buffer, starting at the given start index and at the current position of this buffer. The position of this buffer is then incremented by n.
In other words, an invocation of this method of the form dst.put(src, start, end) has exactly the same effect as the loop
for (int i = start; i < end; i++)
dst.put(src.charAt(i));
except that it first checks that there is sufficient space in this
buffer and it is potentially much more efficient. Invoking this method neither changes nor discards the mark's value.
Invoke this method before a sequence of channel-write or get operations, assuming that the limit has already been set appropriately. For example:
out.write(buf); // Write remaining data buf.rewind(); // Rewind buffer buf.get(array); // Copy data into array
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 characters 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.
CharSequence that is a subsequence of this sequence.
The subsequence starts with the char value at the specified index and
ends with the char value at index end - 1. The length
(in chars) of the
returned sequence is end - start, so if start == end
then an empty sequence is returned. The first character of the resulting string will be the character at this buffer's position, while the last character will be the character at index limit() - 1. Invoking this method does not change the buffer's position.
The current thread must own this object's monitor. The thread
releases ownership of this monitor and waits until another thread
notifies threads waiting on this object's monitor to wake up
either through a call to the notify method or the
notifyAll method. The thread then waits until it can
re-obtain ownership of the monitor and resumes execution.
As in the one argument version, interrupts and spurious wakeups are possible, and this method should always be used in a loop:
synchronized (obj) {
while (<condition does not hold>)
obj.wait();
... // Perform action appropriate to condition
}
This method should only be called by a thread that is the owner
of this object's monitor. See the notify method for a
description of the ways in which a thread can become the owner of
a monitor.The current thread must own this object's monitor.
This method causes the current thread (call it T) to place itself in the wait set for this object and then to relinquish any and all synchronization claims on this object. Thread T becomes disabled for thread scheduling purposes and lies dormant until one of four things happens:
A thread can also wake up without being notified, interrupted, or timing out, a so-called spurious wakeup. While this will rarely occur in practice, applications must guard against it by testing for the condition that should have caused the thread to be awakened, and continuing to wait if the condition is not satisfied. In other words, waits should always occur in loops, like this one:
synchronized (obj) {
while (<condition does not hold>)
obj.wait(timeout);
... // Perform action appropriate to condition
}
(For more information on this topic, see Section 3.2.3 in Doug Lea's
"Concurrent Programming in Java (Second Edition)" (Addison-Wesley,
2000), or Item 50 in Joshua Bloch's "Effective Java Programming
Language Guide" (Addison-Wesley, 2001).
If the current thread is interrupted by another thread while it is waiting, then an InterruptedException is thrown. This exception is not thrown until the lock status of this object has been restored as described above.
Note that the wait method, as it places the current thread into the wait set for this object, unlocks only this object; any other objects on which the current thread may be synchronized remain locked while the thread waits.
This method should only be called by a thread that is the owner
of this object's monitor. See the notify method for a
description of the ways in which a thread can become the owner of
a monitor.
This method is similar to the wait method of one
argument, but it allows finer control over the amount of time to
wait for a notification before giving up. The amount of real time,
measured in nanoseconds, is given by:
1000000*timeout+nanos
In all other respects, this method does the same thing as the method of one argument. In particular, wait(0, 0) means the same thing as wait(0).
The current thread must own this object's monitor. The thread releases ownership of this monitor and waits until either of the following two conditions has occurred:
notify method
or the notifyAll method.
timeout
milliseconds plus nanos nanoseconds arguments, has
elapsed.
The thread then waits until it can re-obtain ownership of the monitor and resumes execution.
As in the one argument version, interrupts and spurious wakeups are possible, and this method should always be used in a loop:
synchronized (obj) {
while (<condition does not hold>)
obj.wait(timeout, nanos);
... // Perform action appropriate to condition
}
This method should only be called by a thread that is the owner
of this object's monitor. See the notify method for a
description of the ways in which a thread can become the owner of
a monitor. The new buffer will be backed by the given character 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.
The new buffer will be backed by the given character 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.
The content of the new, read-only buffer will be the content of the given string. The new buffer's capacity and limit will be csq.length(), its position will be zero, and its mark will be undefined.
The content of the new, read-only buffer will be the content of the given character sequence. The buffer's capacity will be csq.length(), its position will be start, its limit will be end, and its mark will be undefined.