Module java.base
Package java.lang

## Interface CharSequence

- All Known Subinterfaces:
    `Name`
  All Known Implementing Classes:
    `CharBuffer`, `Segment`, `String`, `StringBuffer`, `StringBuilder`

      public interface CharSequence

  A `CharSequence` is a readable sequence of `char` values. This interface provides uniform, read-only access to many different kinds of `char` sequences. A `char` value represents a character in the Basic Multilingual Plane (BMP) or a surrogate. Refer to Unicode Character Representation for details.

  This interface does not refine the general contracts of the `equals` and `hashCode` methods. The result of comparing two objects that implement `CharSequence` is therefore, in general, undefined. Each object may be implemented by a different class, and there is no guarantee that each class will be capable of testing its instances for equality with those of the other. It is therefore inappropriate to use arbitrary `CharSequence` instances as elements in a set or as keys in a map.

  Since:
    1.4

- - ### Method Summary

    All Methods Instance Methods Abstract Methods Default Methods
    Modifier and Type | Method | Description
    --- | --- | ---
    `char` | `charAt​(int index)` | Returns the `char` value at the specified index.
    `default IntStream` | `chars​()` | Returns a stream of `int` zero-extending the `char` values from this sequence.
    `default IntStream` | `codePoints​()` | Returns a stream of code point values from this sequence.
    `int` | `length​()` | Returns the length of this character sequence.
    `CharSequence` | `subSequence​(int start, int end)` | Returns a `CharSequence` that is a subsequence of this sequence.
    `String` | `toString​()` | Returns a string containing the characters in this sequence in the same order as this sequence.

- - ### Method Detail

    - #### length

          int length​()

      Returns the length of this character sequence. The length is the number of 16-bit `char`s in the sequence.
      Returns:
        the number of `char`s in this sequence

    - #### charAt

          char charAt​(int index)

      Returns the `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.

      Parameters:
        `index` - the index of the `char` value to be returned
      Returns:
        the specified `char` value
      Throws:
        `IndexOutOfBoundsException` - if the `index` argument is negative or not less than `length()`

    - #### subSequence

          CharSequence subSequence​(int start,
                                   int end)

      Returns a `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 `char`s) of the returned sequence is `end - start`, so if `start == end` then an empty sequence is returned.
      Parameters:
        `start` - the start index, inclusive
        `end` - the end index, exclusive
      Returns:
        the specified subsequence
      Throws:
        `IndexOutOfBoundsException` - if `start` or `end` are negative, if `end` is greater than `length()`, or if `start` is greater than `end`

    - #### toString

          String toString​()

      Returns a string containing the characters in this sequence in the same order as this sequence. The length of the string will be the length of this sequence.
      Overrides:
        `toString` in class `Object`
      Returns:
        a string consisting of exactly this sequence of characters

    - #### chars

          default IntStream chars​()

      Returns a stream of `int` zero-extending the `char` values from this sequence. Any char which maps to a surrogate code point is passed through uninterpreted.

      The stream binds to this sequence when the terminal stream operation commences (specifically, for mutable sequences the spliterator for the stream is late-binding). If the sequence is modified during that operation then the result is undefined.

      Returns:
        an IntStream of char values from this sequence
      Since:
        1.8

    - #### codePoints

          default IntStream codePoints​()

      Returns a stream of code point values from this sequence. Any surrogate pairs encountered in the sequence are combined as if by Character.toCodePoint and the result is passed to the stream. Any other code units, including ordinary BMP characters, unpaired surrogates, and undefined code units, are zero-extended to `int` values which are then passed to the stream.

      The stream binds to this sequence when the terminal stream operation commences (specifically, for mutable sequences the spliterator for the stream is late-binding). If the sequence is modified during that operation then the result is undefined.

      Returns:
        an IntStream of Unicode code points from this sequence
      Since:
        1.8