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 chars in the sequence.
        Returns:
        the number of chars 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 chars) 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