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>, CharSequence, Appendable, Readable
A buffer of chars.

A char buffer can be created in either one of the following ways:

  • Allocate a new char array and create a buffer based on it;
  • Wrap an existing char array to create a new buffer;
  • Wrap an existing char sequence to create a new buffer;
  • Use ByteBuffer.asCharBuffer to create a char buffer based on a byte buffer.

  • Method Summary

    Modifier and Type Method Description
    static CharBuffer allocate​(int capacity)
    Creates a char buffer based on a newly allocated char array.
    CharBuffer append​(char c)
    Writes the given char to the current position and increases the position by 1.
    CharBuffer append​(CharSequence csq)
    Writes all chars of the given character sequence csq to the current position of this buffer, and increases the position by the length of the csq.
    CharBuffer append​(CharSequence csq, int start, int end)
    Writes chars of the given CharSequence to the current position of this buffer, and increases the position by the number of chars written.
    char[] array()
    Returns the array that backs this buffer (optional operation).
    int arrayOffset()
    Returns the offset into the array returned by array of the first element of the buffer (optional operation).
    abstract CharBuffer asReadOnlyBuffer()
    Returns a read-only buffer that shares its content with this buffer.
    char charAt​(int index)
    Returns the character located at the specified index in the buffer.
    abstract CharBuffer compact()
    Compacts this char buffer.
    int compareTo​(CharBuffer otherBuffer)
    Compare the remaining chars of this buffer to another char buffer's remaining chars.
    abstract CharBuffer duplicate()
    Returns a duplicated buffer that shares its content with this buffer.
    boolean equals​(Object other)
    Checks whether this char buffer is equal to another object.
    abstract char get()
    Returns the char at the current position and increases the position by 1.
    CharBuffer get​(char[] dst)
    Reads chars from the current position into the specified char array and increases the position by the number of chars read.
    CharBuffer get​(char[] dst, int dstOffset, int charCount)
    Reads chars from the current position into the specified char array, starting from the specified offset, and increases the position by the number of chars read.
    abstract char get​(int index)
    Returns a char at the specified index; the position is not changed.
    boolean hasArray()
    Returns true if array and arrayOffset won't throw.
    int hashCode()
    Calculates this buffer's hash code from the remaining chars.
    abstract boolean isDirect()
    Indicates whether this buffer is direct.
    int length()
    Returns the number of remaining chars.
    abstract ByteOrder order()
    Returns the byte order used by this buffer when converting chars from/to bytes.
    abstract CharBuffer put​(char c)
    Writes the given char to the current position and increases the position by 1.
    CharBuffer put​(char[] src)
    Writes chars from the given char array to the current position and increases the position by the number of chars written.
    CharBuffer put​(char[] src, int srcOffset, int charCount)
    Writes chars from the given char array, starting from the specified offset, to the current position and increases the position by the number of chars written.
    abstract CharBuffer put​(int index, char c)
    Writes a char to the specified index of this buffer; the position is not changed.
    CharBuffer put​(String str)
    Writes all chars of the given string to the current position of this buffer, and increases the position by the length of string.
    CharBuffer put​(String str, int start, int end)
    Writes chars of the given string to the current position of this buffer, and increases the position by the number of chars written.
    CharBuffer put​(CharBuffer src)
    Writes all the remaining chars of the src char buffer to this buffer's current position, and increases both buffers' position by the number of chars copied.
    int read​(CharBuffer target)
    Reads characters from this buffer and puts them into target.
    abstract CharBuffer slice()
    Returns a sliced buffer that shares its content with this buffer.
    abstract CharBuffer subSequence​(int start, int end)
    Returns a new char buffer representing a sub-sequence of this buffer's current remaining content.
    String toString()
    Returns a string representing the current remaining chars of this buffer.
    static CharBuffer wrap​(char[] array)
    Creates a new char buffer by wrapping the given char array.
    static CharBuffer wrap​(char[] array, int start, int charCount)
    Creates a new char buffer by wrapping the given char array.
    static CharBuffer wrap​(CharSequence chseq)
    Creates a new char buffer by wrapping the given char sequence.
    static CharBuffer wrap​(CharSequence cs, int start, int end)
    Creates a new char buffer by wrapping the given char sequence.

    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 Details

    • allocate

      public static CharBuffer allocate​(int capacity)
      Creates a char buffer based on a newly allocated char array.
      Parameters:
      capacity - the capacity of the new buffer.
      Returns:
      the created char buffer.
      Throws:
      IllegalArgumentException - if capacity is less than zero.

    • wrap

      public static CharBuffer wrap​(char[] array)
      Creates a new char buffer by wrapping the given char array.

      Calling this method has the same effect as wrap(array, 0, array.length).

      Parameters:
      array - the char array which the new buffer will be based on.
      Returns:
      the created char buffer.

    • wrap

      public static CharBuffer wrap​(char[] array, int start, int charCount)
      Creates a new char buffer by wrapping the given char array.

      The new buffer's position will be start, limit will be start + charCount, capacity will be the length of the array.

      Parameters:
      array - the char array which the new buffer will be based on.
      start - the start index, must not be negative and not greater than array.length.
      charCount - the length, must not be negative and not greater than array.length - start.
      Returns:
      the created char buffer.
      Throws:
      IndexOutOfBoundsException - if either start or charCount is invalid.

    • wrap

      public static CharBuffer wrap​(CharSequence chseq)
      Creates a new char buffer by wrapping the given char sequence.

      Calling this method has the same effect as wrap(chseq, 0, chseq.length()).

      Parameters:
      chseq - the char sequence which the new buffer will be based on.
      Returns:
      the created char buffer.

    • wrap

      public static CharBuffer wrap​(CharSequence cs, int start, int end)
      Creates a new char buffer by wrapping the given char sequence.

      The new buffer's position will be start, limit will be end, capacity will be the length of the char sequence. The new buffer is read-only.

      Parameters:
      cs - the char sequence which the new buffer will be based on.
      start - the start index, must not be negative and not greater than cs.length().
      end - the end index, must be no less than start and no greater than cs.length().
      Returns:
      the created char buffer.
      Throws:
      IndexOutOfBoundsException - if either start or end is invalid.

    • array

      public final char[] array()
      Description copied from class: Buffer
      Returns the array that backs this buffer (optional operation). The returned value is the actual array, not a copy, so modifications to the array write through to the buffer.

      Subclasses should override this method with a covariant return type to provide the exact type of the array.

      Use hasArray to ensure this method won't throw. (A separate call to isReadOnly is not necessary.)

      Specified by:
      array in class Buffer
      Returns:
      the array

    • arrayOffset

      public final int arrayOffset()
      Description copied from class: Buffer
      Returns the offset into the array returned by array of the first element of the buffer (optional operation). The backing array (if there is one) is not necessarily the same size as the buffer, and position 0 in the buffer is not necessarily the 0th element in the array. Use buffer.array()[offset + buffer.arrayOffset() to access element offset in buffer.

      Use hasArray to ensure this method won't throw. (A separate call to isReadOnly is not necessary.)

      Specified by:
      arrayOffset in class Buffer
      Returns:
      the offset

    • asReadOnlyBuffer

      public abstract CharBuffer asReadOnlyBuffer()
      Returns a read-only buffer that shares its content with this buffer.

      The returned buffer is guaranteed to be a new instance, even if this buffer is read-only itself. The new buffer's position, limit, capacity and mark are the same as this buffer's.

      The new buffer shares its content with this buffer, which means this buffer's change of content will be visible to the new buffer. The two buffer's position, limit and mark are independent.

      Returns:
      a read-only version of this buffer.

    • charAt

      public final char charAt​(int index)
      Returns the character located at the specified index in the buffer. The index value is referenced from the current buffer position.
      Specified by:
      charAt in interface CharSequence
      Parameters:
      index - the index referenced from the current buffer position. It must not be less than zero but less than the value obtained from a call to remaining().
      Returns:
      the character located at the specified index (referenced from the current position) in the buffer.
      Throws:
      IndexOutOfBoundsException - if the index is invalid.

    • compact

      public abstract CharBuffer compact()
      Compacts this char buffer.

      The remaining chars will be moved to the head of the buffer, starting from position zero. Then the position is set to remaining(); the limit is set to capacity; the mark is cleared.

      Returns:
      this buffer.
      Throws:
      ReadOnlyBufferException - if no changes may be made to the contents of this buffer.

    • compareTo

      public int compareTo​(CharBuffer otherBuffer)
      Compare the remaining chars of this buffer to another char buffer's remaining chars.
      Specified by:
      compareTo in interface Comparable<CharBuffer>
      Parameters:
      otherBuffer - another char buffer.
      Returns:
      a negative value if this is less than otherBuffer; 0 if this equals to otherBuffer; a positive value if this is greater than otherBuffer.
      Throws:
      ClassCastException - if otherBuffer is not a char buffer.

    • duplicate

      public abstract CharBuffer duplicate()
      Returns a duplicated buffer that shares its content with this buffer.

      The duplicated buffer's initial position, limit, capacity and mark are the same as this buffer's. The duplicated buffer's read-only property and byte order are the same as this buffer's, too.

      The new buffer shares its content with this buffer, which means either buffer's change of content will be visible to the other. The two buffers' position, limit and mark are independent.

    • equals

      public boolean equals​(Object other)
      Checks whether this char buffer is equal to another object.

      If other is not a char buffer then false is returned. Two char buffers are equal if and only if their remaining chars are exactly the same. Position, limit, capacity and mark are not considered.

      Overrides:
      equals in class Object
      Parameters:
      other - the object to compare with this char buffer.
      Returns:
      true if this char buffer is equal to other, false otherwise.
      See Also:
      Object.hashCode()

    • get

      public abstract char get()
      Returns the char at the current position and increases the position by 1.
      Returns:
      the char at the current position.
      Throws:
      BufferUnderflowException - if the position is equal or greater than limit.

    • get

      public CharBuffer get​(char[] dst)
      Reads chars from the current position into the specified char array and increases the position by the number of chars read.

      Calling this method has the same effect as get(dst, 0, dst.length).

      Parameters:
      dst - the destination char array.
      Returns:
      this buffer.
      Throws:
      BufferUnderflowException - if dst.length is greater than remaining().

    • get

      public CharBuffer get​(char[] dst, int dstOffset, int charCount)
      Reads chars from the current position into the specified char array, starting from the specified offset, and increases the position by the number of chars read.
      Parameters:
      dst - the target char array.
      dstOffset - the offset of the char array, must not be negative and not greater than dst.length.
      charCount - The number of chars to read, must be no less than zero and no greater than dst.length - dstOffset.
      Returns:
      this buffer.
      Throws:
      IndexOutOfBoundsException - if either dstOffset or charCount is invalid.
      BufferUnderflowException - if charCount is greater than remaining().

    • get

      public abstract char get​(int index)
      Returns a char at the specified index; the position is not changed.
      Parameters:
      index - the index, must not be negative and less than limit.
      Returns:
      a char at the specified index.
      Throws:
      IndexOutOfBoundsException - if index is invalid.

    • hasArray

      public final boolean hasArray()
      Description copied from class: Buffer
      Returns true if array and arrayOffset won't throw. This method does not return true for buffers not backed by arrays because the other methods would throw UnsupportedOperationException, nor does it return true for buffers backed by read-only arrays, because the other methods would throw ReadOnlyBufferException.
      Specified by:
      hasArray in class Buffer

    • hashCode

      public int hashCode()
      Calculates this buffer's hash code from the remaining chars. The position, limit, capacity and mark don't affect the hash code.
      Overrides:
      hashCode in class Object
      Returns:
      the hash code calculated from the remaining chars.
      See Also:
      Object.equals(java.lang.Object)

    • isDirect

      public abstract boolean isDirect()
      Indicates whether this buffer is direct. A direct buffer will try its best to take advantage of native memory APIs and it may not stay in the Java heap, so it is not affected by garbage collection.

      A char buffer is direct if it is based on a byte buffer and the byte buffer is direct.

      Specified by:
      isDirect in class Buffer
      Returns:
      true if this buffer is direct, false otherwise.

    • length

      public final int length()
      Returns the number of remaining chars.
      Specified by:
      length in interface CharSequence
      Returns:
      the number of remaining chars.

    • order

      public abstract ByteOrder order()
      Returns the byte order used by this buffer when converting chars from/to bytes.

      If this buffer is not based on a byte buffer, then this always returns the platform's native byte order.

      Returns:
      the byte order used by this buffer when converting chars from/to bytes.

    • put

      public abstract CharBuffer put​(char c)
      Writes the given char to the current position and increases the position by 1.
      Parameters:
      c - the char to write.
      Returns:
      this buffer.
      Throws:
      BufferOverflowException - if position is equal or greater than limit.
      ReadOnlyBufferException - if no changes may be made to the contents of this buffer.

    • put

      public final CharBuffer put​(char[] src)
      Writes chars from the given char array to the current position and increases the position by the number of chars written.

      Calling this method has the same effect as put(src, 0, src.length).

      Parameters:
      src - the source char array.
      Returns:
      this buffer.
      Throws:
      BufferOverflowException - if remaining() is less than src.length.
      ReadOnlyBufferException - if no changes may be made to the contents of this buffer.

    • put

      public CharBuffer put​(char[] src, int srcOffset, int charCount)
      Writes chars from the given char array, starting from the specified offset, to the current position and increases the position by the number of chars written.
      Parameters:
      src - the source char array.
      srcOffset - the offset of char array, must not be negative and not greater than src.length.
      charCount - the number of chars to write, must be no less than zero and no greater than src.length - srcOffset.
      Returns:
      this buffer.
      Throws:
      BufferOverflowException - if remaining() is less than charCount.
      IndexOutOfBoundsException - if either srcOffset or charCount is invalid.
      ReadOnlyBufferException - if no changes may be made to the contents of this buffer.

    • put

      public CharBuffer put​(CharBuffer src)
      Writes all the remaining chars of the src char buffer to this buffer's current position, and increases both buffers' position by the number of chars copied.
      Parameters:
      src - the source char buffer.
      Returns:
      this buffer.
      Throws:
      BufferOverflowException - if src.remaining() is greater than this buffer's remaining().
      IllegalArgumentException - if src is this buffer.
      ReadOnlyBufferException - if no changes may be made to the contents of this buffer.

    • put

      public abstract CharBuffer put​(int index, char c)
      Writes a char to the specified index of this buffer; the position is not changed.
      Parameters:
      index - the index, must be no less than zero and less than the limit.
      c - the char to write.
      Returns:
      this buffer.
      Throws:
      IndexOutOfBoundsException - if index is invalid.
      ReadOnlyBufferException - if no changes may be made to the contents of this buffer.

    • put

      public final CharBuffer put​(String str)
      Writes all chars of the given string to the current position of this buffer, and increases the position by the length of string.

      Calling this method has the same effect as put(str, 0, str.length()).

      Parameters:
      str - the string to write.
      Returns:
      this buffer.
      Throws:
      BufferOverflowException - if remaining() is less than the length of string.
      ReadOnlyBufferException - if no changes may be made to the contents of this buffer.

    • put

      public CharBuffer put​(String str, int start, int end)
      Writes chars of the given string to the current position of this buffer, and increases the position by the number of chars written.
      Parameters:
      str - the string to write.
      start - the first char to write, must not be negative and not greater than str.length().
      end - the last char to write (excluding), must be less than start and not greater than str.length().
      Returns:
      this buffer.
      Throws:
      BufferOverflowException - if remaining() is less than end - start.
      IndexOutOfBoundsException - if either start or end is invalid.
      ReadOnlyBufferException - if no changes may be made to the contents of this buffer.

    • slice

      public abstract CharBuffer slice()
      Returns a sliced buffer that shares its content with this buffer.

      The sliced buffer's capacity will be this buffer's remaining(), and its zero position will correspond to this buffer's current position. The new buffer's position will be 0, limit will be its capacity, and its mark is cleared. The new buffer's read-only property and byte order are same as this buffer.

      The new buffer shares its content with this buffer, which means either buffer's change of content will be visible to the other. The two buffers' position, limit and mark are independent.

    • subSequence

      public abstract CharBuffer subSequence​(int start, int end)
      Returns a new char buffer representing a sub-sequence of this buffer's current remaining content.

      The new buffer's position will be position() + start, limit will be position() + end, capacity will be the same as this buffer. The new buffer's read-only property and byte order are the same as this buffer.

      The new buffer shares its content with this buffer, which means either buffer's change of content will be visible to the other. The two buffers' position, limit and mark are independent.

      Specified by:
      subSequence in interface CharSequence
      Parameters:
      start - the start index of the sub-sequence, referenced from the current buffer position. Must not be less than zero and not greater than the value obtained from a call to remaining().
      end - the end index of the sub-sequence, referenced from the current buffer position. Must not be less than start and not be greater than the value obtained from a call to remaining().
      Returns:
      a new char buffer represents a sub-sequence of this buffer's current remaining content.
      Throws:
      IndexOutOfBoundsException - if either start or end is invalid.

    • toString

      public String toString()
      Returns a string representing the current remaining chars of this buffer.
      Specified by:
      toString in interface CharSequence
      Overrides:
      toString in class Buffer
      Returns:
      a printable representation of this object.

    • append

      public CharBuffer append​(char c)
      Writes the given char to the current position and increases the position by 1.
      Specified by:
      append in interface Appendable
      Parameters:
      c - the char to write.
      Returns:
      this buffer.
      Throws:
      BufferOverflowException - if position is equal or greater than limit.
      ReadOnlyBufferException - if no changes may be made to the contents of this buffer.

    • append

      public CharBuffer append​(CharSequence csq)
      Writes all chars of the given character sequence csq to the current position of this buffer, and increases the position by the length of the csq.

      Calling this method has the same effect as append(csq.toString()). If the CharSequence is null the string "null" will be written to the buffer.

      Specified by:
      append in interface Appendable
      Parameters:
      csq - the CharSequence to write.
      Returns:
      this buffer.
      Throws:
      BufferOverflowException - if remaining() is less than the length of csq.
      ReadOnlyBufferException - if no changes may be made to the contents of this buffer.

    • append

      public CharBuffer append​(CharSequence csq, int start, int end)
      Writes chars of the given CharSequence to the current position of this buffer, and increases the position by the number of chars written.
      Specified by:
      append in interface Appendable
      Parameters:
      csq - the CharSequence to write.
      start - the first char to write, must not be negative and not greater than csq.length().
      end - the last char to write (excluding), must be less than start and not greater than csq.length().
      Returns:
      this buffer.
      Throws:
      BufferOverflowException - if remaining() is less than end - start.
      IndexOutOfBoundsException - if either start or end is invalid.
      ReadOnlyBufferException - if no changes may be made to the contents of this buffer.

    • read

      public int read​(CharBuffer target) throws IOException
      Reads characters from this buffer and puts them into target. The number of chars that are copied is either the number of remaining chars in this buffer or the number of remaining chars in target, whichever is smaller.
      Specified by:
      read in interface Readable
      Parameters:
      target - the target char buffer.
      Returns:
      the number of chars copied or -1 if there are no chars left to be read from this buffer.
      Throws:
      IllegalArgumentException - if target is this buffer.
      IOException - if an I/O error occurs.
      ReadOnlyBufferException - if no changes may be made to the contents of target.