com.google.common.escape

## Class CharEscaper

- java.lang.Object
- - com.google.common.escape.Escaper
  - - com.google.common.escape.CharEscaper

- Direct Known Subclasses:
    ArrayBasedCharEscaper

      @Beta
      @GwtCompatible
      public abstract class CharEscaper
      extends Escaper

  An object that converts literal text into a format safe for inclusion in a particular context (such as an XML document). Typically (but not always), the inverse process of "unescaping" the text is performed automatically by the relevant parser.

  For example, an XML escaper would convert the literal string `"Foo<Bar>"` into `"Foo&lt;Bar&gt;"` to prevent `"<Bar>"` from being confused with an XML tag. When the resulting XML document is parsed, the parser API will return this text as the original literal string `"Foo<Bar>"`.

  A `CharEscaper` instance is required to be stateless, and safe when used concurrently by multiple threads.

  Popular escapers are defined as constants in classes like `HtmlEscapers` and `XmlEscapers`. To create your own escapers extend this class and implement the `escape(char)` method.

  Since:
    15.0

- - ### Constructor Summary

    Constructors
    Modifier | Constructor and Description
    --- | ---
    `protected` | `CharEscaper()` Constructor for use by subclasses.

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `protected abstract char[]` | `escape(char c)` Returns the escaped form of the given character, or `null` if this character does not need to be escaped.
    `java.lang.String` | `escape(java.lang.String string)` Returns the escaped form of a given literal string.
    `protected java.lang.String` | `escapeSlow(java.lang.String s, int index)` Returns the escaped form of a given literal string, starting at the given index.

    - ### Methods inherited from class com.google.common.escape.Escaper

      `asFunction`

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### CharEscaper

          protected CharEscaper()

      Constructor for use by subclasses.

  - ### Method Detail

    - #### escape

          public java.lang.String escape(java.lang.String string)

      Returns the escaped form of a given literal string.
      Specified by:
        `escape` in class `Escaper`
      Parameters:
        `string` - the literal string to be escaped
      Returns:
        the escaped form of `string`
      Throws:
        `java.lang.NullPointerException` - if `string` is null

    - #### escapeSlow

          protected final java.lang.String escapeSlow(java.lang.String s,
                                    int index)

      Returns the escaped form of a given literal string, starting at the given index. This method is called by the `escape(String)` method when it discovers that escaping is required. It is protected to allow subclasses to override the fastpath escaping function to inline their escaping test. See `CharEscaperBuilder` for an example usage.
      Parameters:
        `s` - the literal string to be escaped
        `index` - the index to start escaping from
      Returns:
        the escaped form of `string`
      Throws:
        `java.lang.NullPointerException` - if `string` is null

    - #### escape

          protected abstract char[] escape(char c)

      Returns the escaped form of the given character, or `null` if this character does not need to be escaped. If an empty array is returned, this effectively strips the input character from the resulting text.

      If the character does not need to be escaped, this method should return `null`, rather than a one-character array containing the character itself. This enables the escaping algorithm to perform more efficiently.

      An escaper is expected to be able to deal with any `char` value, so this method should not throw any exceptions.

      Parameters:
        `c` - the character to escape if necessary
      Returns:
        the replacement characters, or `null` if no escaping was needed