Module java.base
Package java.nio

Class CharBuffer

java.lang.Object
java.nio.Buffer
java.nio.CharBuffer
All Implemented Interfaces:
Appendable, CharSequence, Comparable<CharBuffer>, Readable
public abstract class CharBuffer
extends Buffer
implements Comparable<CharBuffer>, Appendable, CharSequence, Readable
A char buffer.

This class defines four categories of operations upon char buffers:

  • Absolute and relative get and put methods that read and write single chars;

  • Absolute and relative bulk get methods that transfer contiguous sequences of chars from this buffer into an array; and

  • Absolute and relative bulk put methods that transfer contiguous sequences of chars from a char array, a string, or some other char buffer into this buffer; and

  • A method for compacting a char buffer.

Char buffers can be created either by allocation, which allocates space for the buffer's content, by wrapping an existing char array or string into a buffer, or by creating a view of an existing byte buffer.

Like a byte buffer, a char buffer is either direct or non-direct. A char buffer created via the wrap methods of this class will be non-direct. A char 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 char 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. The methods defined by CharSequence operate relative to the current position of the buffer when they are invoked.

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);
can, for example, be replaced by the single statement 
 cb.put("text/").put(subtype).put("; charset=").put(enc);

Since:
1.4

  • Method Summary

    Modifier and Type Method Description
    static CharBuffer allocate​(int capacity)
    Allocates a new char buffer.
    CharBuffer append​(char c)
    Appends the specified char to this buffer  (optional operation).
    CharBuffer append​(CharSequence csq)
    Appends the specified character sequence to this buffer  (optional operation).
    CharBuffer append​(CharSequence csq, int start, int end)
    Appends a subsequence of the specified character sequence to this buffer  (optional operation).
    char[] array()
    Returns the char 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 asReadOnlyBuffer()
    Creates a new, read-only char buffer that shares this buffer's content.
    char charAt​(int index)
    Reads the character at the given index relative to the current position.
    CharBuffer clear()
    Clears this buffer.
    abstract CharBuffer compact()
    Compacts this buffer  (optional operation).
    int compareTo​(CharBuffer that)
    Compares this buffer to another.
    abstract CharBuffer duplicate()
    Creates a new char buffer that shares this buffer's content.
    boolean equals​(Object ob)
    Tells whether or not this buffer is equal to another object.
    CharBuffer flip()
    Flips this buffer.
    abstract char get()
    Relative get method.
    CharBuffer get​(char[] dst)
    Relative bulk get method.
    CharBuffer get​(char[] dst, int offset, int length)
    Relative bulk get method.
    abstract char get​(int index)
    Absolute get method.
    CharBuffer get​(int index, char[] dst)
    Absolute bulk get method.
    CharBuffer get​(int index, char[] dst, int offset, int length)
    Absolute bulk get method.
    boolean hasArray()
    Tells whether or not this buffer is backed by an accessible char array.
    int hashCode()
    Returns the current hash code of this buffer.
    abstract boolean isDirect()
    Tells whether or not this char buffer is direct.
    int length()
    Returns the length of this character buffer.
    CharBuffer limit​(int newLimit)
    Sets this buffer's limit.
    CharBuffer mark()
    Sets this buffer's mark at its position.
    int mismatch​(CharBuffer that)
    Finds and returns the relative index of the first mismatch between this buffer and a given buffer.
    abstract ByteOrder order()
    Retrieves this buffer's byte order.
    CharBuffer position​(int newPosition)
    Sets this buffer's position.
    abstract CharBuffer put​(char c)
    Relative put method  (optional operation).
    CharBuffer put​(char[] src)
    Relative bulk put method  (optional operation).
    CharBuffer put​(char[] src, int offset, int length)
    Relative bulk put method  (optional operation).
    abstract CharBuffer put​(int index, char c)
    Absolute put method  (optional operation).
    CharBuffer put​(int index, char[] src)
    Absolute bulk put method  (optional operation).
    CharBuffer put​(int index, char[] src, int offset, int length)
    Absolute bulk put method  (optional operation).
    CharBuffer put​(String src)
    Relative bulk put method  (optional operation).
    CharBuffer put​(String src, int start, int end)
    Relative bulk put method  (optional operation).
    CharBuffer put​(CharBuffer src)
    Relative bulk put method  (optional operation).
    int read​(CharBuffer target)
    Attempts to read characters into the specified character buffer.
    CharBuffer reset()
    Resets this buffer's position to the previously-marked position.
    CharBuffer rewind()
    Rewinds this buffer.
    abstract CharBuffer slice()
    Creates a new char buffer whose content is a shared subsequence of this buffer's content.
    abstract CharBuffer slice​(int index, int length)
    Creates a new char buffer whose content is a shared subsequence of this buffer's content.
    abstract CharBuffer subSequence​(int start, int end)
    Creates a new character buffer that represents the specified subsequence of this buffer, relative to the current position.
    String toString()
    Returns a string containing the characters in this buffer.
    static CharBuffer wrap​(char[] array)
    Wraps a char array into a buffer.
    static CharBuffer wrap​(char[] array, int offset, int length)
    Wraps a char array into a buffer.
    static CharBuffer wrap​(CharSequence csq)
    Wraps a character sequence into a buffer.
    static CharBuffer wrap​(CharSequence csq, int start, int end)
    Wraps a character sequence into a buffer.

    Methods declared in class java.nio.Buffer

    capacity, hasRemaining, isReadOnly, limit, position, remaining

    Methods declared in class java.lang.Object

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

    Methods declared in interface java.lang.CharSequence

    chars, codePoints

  • Method Details

    • allocate

      public static CharBuffer allocate​(int capacity)
      Allocates a new char buffer.

      The new buffer's position will be zero, its limit will be its capacity, its mark will be undefined, each of its elements will be initialized to zero, and its byte order will be the native order of the underlying hardware. It will have a backing array, and its array offset will be zero.

      Parameters:
      capacity - The new buffer's capacity, in chars
      Returns:
      The new char buffer
      Throws:
      IllegalArgumentException - If the capacity is a negative integer

    • wrap

      public static CharBuffer wrap​(char[] array, int offset, int length)
      Wraps a char array into a buffer.

      The new buffer will be backed by the given char 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, its mark will be undefined, and its byte order will be the native order of the underlying hardware. 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 char buffer
      Throws:
      IndexOutOfBoundsException - If the preconditions on the offset and length parameters do not hold

    • wrap

      public static CharBuffer wrap​(char[] array)
      Wraps a char array into a buffer.

      The new buffer will be backed by the given char 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, its mark will be undefined, and its byte order will be the native order of the underlying hardware. 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 char buffer

    • read

      public int read​(CharBuffer target) throws IOException
      Attempts to read characters into the specified character buffer. The buffer is used as a repository of characters as-is: the only changes made are the results of a put operation. No flipping or rewinding of the buffer is performed.
      Specified by:
      read in interface Readable
      Parameters:
      target - the buffer to read characters into
      Returns:
      The number of characters added to the buffer, or -1 if this source of characters is at its end
      Throws:
      IOException - if an I/O error occurs
      ReadOnlyBufferException - if target is a read only buffer
      Since:
      1.5

    • wrap

      public static CharBuffer wrap​(CharSequence csq, int start, int end)
      Wraps a character sequence into a buffer.

      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.

      Parameters:
      csq - The character sequence from which the new character buffer is to be created
      start - The index of the first character to be used; must be non-negative and no larger than csq.length(). The new buffer's position will be set to this value.
      end - The index of the character following the last character to be used; must be no smaller than start and no larger than csq.length(). The new buffer's limit will be set to this value.
      Returns:
      The new character buffer
      Throws:
      IndexOutOfBoundsException - If the preconditions on the start and end parameters do not hold

    • wrap

      public static CharBuffer wrap​(CharSequence csq)
      Wraps a character sequence into a buffer.

      The content of the new, read-only buffer will be the content of the given character sequence. The new buffer's capacity and limit will be csq.length(), its position will be zero, and its mark will be undefined.

      Parameters:
      csq - The character sequence from which the new character buffer is to be created
      Returns:
      The new character buffer

    • slice

      public abstract CharBuffer slice()
      Creates a new char 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 chars remaining in this buffer, its mark will be undefined, and its byte order will be identical to that 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.

      Specified by:
      slice in class Buffer
      Returns:
      The new char buffer

    • slice

      public abstract CharBuffer slice​(int index, int length)
      Creates a new char buffer whose content is a shared subsequence of this buffer's content.

      The content of the new buffer will start at position index in this buffer, and will contain length elements. 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 length, its mark will be undefined, and its byte order will be identical to that 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.

      Specified by:
      slice in class Buffer
      Parameters:
      index - The position in this buffer at which the content of the new buffer will start; must be non-negative and no larger than limit()
      length - The number of elements the new buffer will contain; must be non-negative and no larger than limit() - index
      Returns:
      The new buffer
      Throws:
      IndexOutOfBoundsException - If index is negative or greater than limit(), length is negative, or length > limit() - index
      Since:
      13

    • duplicate

      public abstract CharBuffer duplicate()
      Creates a new char 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, mark values, and byte order 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.

      Specified by:
      duplicate in class Buffer
      Returns:
      The new char buffer

    • asReadOnlyBuffer

      public abstract CharBuffer asReadOnlyBuffer()
      Creates a new, read-only char 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, mark values, and byte order 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 char buffer

    • get

      public abstract char get()
      Relative get method. Reads the char at this buffer's current position, and then increments the position.
      Returns:
      The char at the buffer's current position
      Throws:
      BufferUnderflowException - If the buffer's current position is not smaller than its limit

    • put

      public abstract CharBuffer put​(char c)
      Relative put method  (optional operation).

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

      Parameters:
      c - The char 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 char get​(int index)
      Absolute get method. Reads the char at the given index.
      Parameters:
      index - The index from which the char will be read
      Returns:
      The char at the given index
      Throws:
      IndexOutOfBoundsException - If index is negative or not smaller than the buffer's limit

    • put

      public abstract CharBuffer put​(int index, char c)
      Absolute put method  (optional operation).

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

      Parameters:
      index - The index at which the char will be written
      c - The char 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 CharBuffer get​(char[] dst, int offset, int length)
      Relative bulk get method.

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

      Otherwise, this method copies length chars 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 chars in this buffer and it is potentially much more efficient.

      Parameters:
      dst - The array into which chars are to be written
      offset - The offset within the array of the first char to be written; must be non-negative and no larger than dst.length
      length - The maximum number of chars 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 chars remaining in this buffer
      IndexOutOfBoundsException - If the preconditions on the offset and length parameters do not hold

    • get

      public CharBuffer get​(char[] dst)
      Relative bulk get method.

      This method transfers chars 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)

      Parameters:
      dst - The destination array
      Returns:
      This buffer
      Throws:
      BufferUnderflowException - If there are fewer than length chars remaining in this buffer

    • get

      public CharBuffer get​(int index, char[] dst, int offset, int length)
      Absolute bulk get method.

      This method transfers length chars from this buffer into the given array, starting at the given index in this buffer and at the given offset in the array. The position of this buffer is unchanged.

      An invocation of this method of the form src.get(index, dst, offset, length) has exactly the same effect as the following loop except that it first checks the consistency of the supplied parameters and it is potentially much more efficient: 

      
     for (int i = offset, j = index; i < offset + length; i++, j++)
         dst[i] = src.get(j);

      Parameters:
      index - The index in this buffer from which the first char will be read; must be non-negative and less than limit()
      dst - The destination array
      offset - The offset within the array of the first char to be written; must be non-negative and less than dst.length
      length - The number of chars to be written to the given array; must be non-negative and no larger than the smaller of limit() - index and dst.length - offset
      Returns:
      This buffer
      Throws:
      IndexOutOfBoundsException - If the preconditions on the index, offset, and length parameters do not hold
      Since:
      13

    • get

      public CharBuffer get​(int index, char[] dst)
      Absolute bulk get method.

      This method transfers chars from this buffer into the given destination array. The position of this buffer is unchanged. An invocation of this method of the form src.get(index, dst) behaves in exactly the same way as the invocation: 

           src.get(index, dst, 0, dst.length)

      Parameters:
      index - The index in this buffer from which the first char will be read; must be non-negative and less than limit()
      dst - The destination array
      Returns:
      This buffer
      Throws:
      IndexOutOfBoundsException - If index is negative, not smaller than limit(), or limit() - index < dst.length
      Since:
      13

    • put

      public CharBuffer put​(CharBuffer src)
      Relative bulk put method  (optional operation).

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

      Otherwise, this method copies n = src.remaining() chars 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 chars 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 chars in the source buffer
      IllegalArgumentException - If the source buffer is this buffer
      ReadOnlyBufferException - If this buffer is read-only

    • put

      public CharBuffer put​(char[] src, int offset, int length)
      Relative bulk put method  (optional operation).

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

      Otherwise, this method copies length chars 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(src[i]);
      except that it first checks that there is sufficient space in this buffer and it is potentially much more efficient.

      Parameters:
      src - The array from which chars are to be read
      offset - The offset within the array of the first char to be read; must be non-negative and no larger than src.length
      length - The number of chars to be read from the given array; must be non-negative and no larger than src.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 CharBuffer put​(char[] src)
      Relative bulk put method  (optional operation).

      This method transfers the entire content of the given source char 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)

      Parameters:
      src - The source array
      Returns:
      This buffer
      Throws:
      BufferOverflowException - If there is insufficient space in this buffer
      ReadOnlyBufferException - If this buffer is read-only

    • put

      public CharBuffer put​(int index, char[] src, int offset, int length)
      Absolute bulk put method  (optional operation).

      This method transfers length chars from the given array, starting at the given offset in the array and at the given index in this buffer. The position of this buffer is unchanged.

      An invocation of this method of the form dst.put(index, src, offset, length) has exactly the same effect as the following loop except that it first checks the consistency of the supplied parameters and it is potentially much more efficient: 

      
     for (int i = offset, j = index; i < offset + length; i++, j++)
         dst.put(j, src[i]);

      Parameters:
      index - The index in this buffer at which the first char will be written; must be non-negative and less than limit()
      src - The array from which chars are to be read
      offset - The offset within the array of the first char to be read; must be non-negative and less than src.length
      length - The number of chars to be read from the given array; must be non-negative and no larger than the smaller of limit() - index and src.length - offset
      Returns:
      This buffer
      Throws:
      IndexOutOfBoundsException - If the preconditions on the index, offset, and length parameters do not hold
      ReadOnlyBufferException - If this buffer is read-only
      Since:
      13

    • put

      public CharBuffer put​(int index, char[] src)
      Absolute bulk put method  (optional operation).

      This method copies chars into this buffer from the given source array. The position of this buffer is unchanged. An invocation of this method of the form dst.put(index, src) behaves in exactly the same way as the invocation: 

           dst.put(index, src, 0, src.length);

      Parameters:
      index - The index in this buffer at which the first char will be written; must be non-negative and less than limit()
      src - The array from which chars are to be read
      Returns:
      This buffer
      Throws:
      IndexOutOfBoundsException - If index is negative, not smaller than limit(), or limit() - index < src.length
      ReadOnlyBufferException - If this buffer is read-only
      Since:
      13

    • put

      public CharBuffer put​(String src, int start, int end)
      Relative bulk put method  (optional operation).

      This method transfers chars from the given string into this buffer. If there are more chars to be copied from the string than remain in this buffer, that is, if end - start > remaining(), then no chars are transferred and a BufferOverflowException is thrown.

      Otherwise, this method copies n = end - start chars 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.

      Parameters:
      src - The string from which chars are to be read
      start - The offset within the string of the first char to be read; must be non-negative and no larger than string.length()
      end - The offset within the string of the last char to be read, plus one; must be non-negative and no larger than string.length()
      Returns:
      This buffer
      Throws:
      BufferOverflowException - If there is insufficient space in this buffer
      IndexOutOfBoundsException - If the preconditions on the start and end parameters do not hold
      ReadOnlyBufferException - If this buffer is read-only

    • put

      public final CharBuffer put​(String src)
      Relative bulk put method  (optional operation).

      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())

      Parameters:
      src - The source string
      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 char array.

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

      Specified by:
      hasArray in class Buffer
      Returns:
      true if, and only if, this buffer is backed by an array and is not read-only

    • array

      public final char[] array()
      Returns the char 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.

      Specified by:
      array in class Buffer
      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.

      Specified by:
      arrayOffset in class Buffer
      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

    • position

      public final CharBuffer position​(int newPosition)
      Sets this buffer's position. If the mark is defined and larger than the new position then it is discarded.
      Overrides:
      position in class Buffer
      Parameters:
      newPosition - The new position value; must be non-negative and no larger than the current limit
      Returns:
      This buffer

    • limit

      public final CharBuffer limit​(int newLimit)
      Sets this buffer's limit. If the position is larger than the new limit then it is set to the new limit. If the mark is defined and larger than the new limit then it is discarded.
      Overrides:
      limit in class Buffer
      Parameters:
      newLimit - The new limit value; must be non-negative and no larger than this buffer's capacity
      Returns:
      This buffer

    • mark

      public final CharBuffer mark()
      Sets this buffer's mark at its position.
      Overrides:
      mark in class Buffer
      Returns:
      This buffer

    • reset

      public final CharBuffer reset()
      Resets this buffer's position to the previously-marked position.

      Invoking this method neither changes nor discards the mark's value.

      Overrides:
      reset in class Buffer
      Returns:
      This buffer

    • clear

      public final CharBuffer clear()
      Clears this buffer. The position is set to zero, the limit is set to the capacity, and the mark is discarded.

      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.

      Overrides:
      clear in class Buffer
      Returns:
      This buffer

    • flip

      public final CharBuffer flip()
      Flips this buffer. The limit is set to the current position and then the position is set to zero. If the mark is defined then it is discarded.

      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.

      Overrides:
      flip in class Buffer
      Returns:
      This buffer

    • rewind

      public final CharBuffer rewind()
      Rewinds this buffer. The position is set to zero and the mark is discarded.

      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

      Overrides:
      rewind in class Buffer
      Returns:
      This buffer

    • compact

      public abstract CharBuffer compact()
      Compacts this buffer  (optional operation).

      The chars between the buffer's current position and its limit, if any, are copied to the beginning of the buffer. That is, the char at index p = position() is copied to index zero, the char at index p + 1 is copied to index one, and so forth until the char 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 chars copied, rather than to zero, so that an invocation of this method can be followed immediately by an invocation of another relative put method.

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

    • isDirect

      public abstract boolean isDirect()
      Tells whether or not this char buffer is direct.
      Specified by:
      isDirect in class Buffer
      Returns:
      true if, and only if, this buffer is direct

    • hashCode

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

      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.

      Overrides:
      hashCode in class Object
      Returns:
      The current hash code of this buffer
      See Also:
      Object.equals(java.lang.Object), System.identityHashCode(java.lang.Object)

    • equals

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

      Two char buffers are equal if, and only if,

      1. They have the same element type,

      2. They have the same number of remaining elements, and

      3. 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.

      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(), HashMap

    • compareTo

      public int compareTo​(CharBuffer that)
      Compares this buffer to another.

      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. Pairs of char elements are compared as if by invoking Character.compare(char,char).

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

      Specified by:
      compareTo in interface Comparable<CharBuffer>
      Parameters:
      that - 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

    • mismatch

      public int mismatch​(CharBuffer that)
      Finds and returns the relative index of the first mismatch between this buffer and a given buffer. The index is relative to the position of each buffer and will be in the range of 0 (inclusive) up to the smaller of the remaining elements in each buffer (exclusive).

      If the two buffers share a common prefix then the returned index is the length of the common prefix and it follows that there is a mismatch between the two buffers at that index within the respective buffers. If one buffer is a proper prefix of the other then the returned index is the smaller of the remaining elements in each buffer, and it follows that the index is only valid for the buffer with the larger number of remaining elements. Otherwise, there is no mismatch.

      Parameters:
      that - The byte buffer to be tested for a mismatch with this buffer
      Returns:
      The relative index of the first mismatch between this and the given buffer, otherwise -1 if no mismatch.
      Since:
      11

    • toString

      public String toString()
      Returns a string containing the characters in this buffer.

      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.

      Specified by:
      toString in interface CharSequence
      Overrides:
      toString in class Object
      Returns:
      The specified string

    • length

      public final int length()
      Returns the length of this character buffer.

      When viewed as a character sequence, the length of a character buffer is simply the number of characters between the position (inclusive) and the limit (exclusive); that is, it is equivalent to remaining().

      Specified by:
      length in interface CharSequence
      Returns:
      The length of this character buffer

    • charAt

      public final char charAt​(int index)
      Reads the character at the given index relative to the current position.
      Specified by:
      charAt in interface CharSequence
      Parameters:
      index - The index of the character to be read, relative to the position; must be non-negative and smaller than remaining()
      Returns:
      The character at index position() + index
      Throws:
      IndexOutOfBoundsException - If the preconditions on index do not hold

    • subSequence

      public abstract CharBuffer subSequence​(int start, int end)
      Creates a new character buffer that represents the specified subsequence of this buffer, relative to the current position.

      The new buffer will share this buffer's content; that is, if the content of this buffer is mutable then modifications to one buffer will cause the other to be modified. The new buffer's capacity will be that of this buffer, its position will be position() + start, and its limit will be position() + end. 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.

      Specified by:
      subSequence in interface CharSequence
      Parameters:
      start - The index, relative to the current position, of the first character in the subsequence; must be non-negative and no larger than remaining()
      end - The index, relative to the current position, of the character following the last character in the subsequence; must be no smaller than start and no larger than remaining()
      Returns:
      The new character buffer
      Throws:
      IndexOutOfBoundsException - If the preconditions on start and end do not hold

    • append

      public CharBuffer append​(CharSequence csq)
      Appends the specified character sequence to this buffer  (optional operation).

      An invocation of this method of the form dst.append(csq) behaves in exactly the same way as the invocation 

           dst.put(csq.toString())

      Depending on the specification of toString for the character sequence csq, the entire sequence may not be appended. For instance, invoking the toString method of a character buffer will return a subsequence whose content depends upon the buffer's position and limit.

      Specified by:
      append in interface Appendable
      Parameters:
      csq - The character sequence to append. If csq is null, then the four characters "null" are appended to this character buffer.
      Returns:
      This buffer
      Throws:
      BufferOverflowException - If there is insufficient space in this buffer
      ReadOnlyBufferException - If this buffer is read-only
      Since:
      1.5

    • append

      public CharBuffer append​(CharSequence csq, int start, int end)
      Appends a subsequence of the specified character sequence to this buffer  (optional operation).

      An invocation of this method of the form dst.append(csq, start, end) when csq is not null, behaves in exactly the same way as the invocation 

           dst.put(csq.subSequence(start, end).toString())

      Specified by:
      append in interface Appendable
      Parameters:
      csq - The character sequence from which a subsequence will be appended. If csq is null, then characters will be appended as if csq contained the four characters "null".
      start - The index of the first character in the subsequence
      end - The index of the character following the last character in the subsequence
      Returns:
      This buffer
      Throws:
      BufferOverflowException - If there is insufficient space in this buffer
      IndexOutOfBoundsException - If start or end are negative, start is greater than end, or end is greater than csq.length()
      ReadOnlyBufferException - If this buffer is read-only
      Since:
      1.5

    • append

      public CharBuffer append​(char c)
      Appends the specified char to this buffer  (optional operation).

      An invocation of this method of the form dst.append(c) behaves in exactly the same way as the invocation 

           dst.put(c)

      Specified by:
      append in interface Appendable
      Parameters:
      c - The 16-bit char to append
      Returns:
      This buffer
      Throws:
      BufferOverflowException - If there is insufficient space in this buffer
      ReadOnlyBufferException - If this buffer is read-only
      Since:
      1.5

    • order

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

      The byte order of a char buffer created by allocation or by wrapping an existing char array is the native order of the underlying hardware. The byte order of a char buffer created as a view of a byte buffer is that of the byte buffer at the moment that the view is created.

      Returns:
      This buffer's byte order