Text (Hadoop 1.2.1 API)
Date: 2013-07-22

Overview | Package | Class | Use | Tree | Deprecated | Index | Help
PREV CLASS NEXT CLASS | FRAMES NO FRAMES
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD

## org.apache.hadoop.io
Class Text

    java.lang.Object
      org.apache.hadoop.io.BinaryComparable
          org.apache.hadoop.io.Text

All Implemented Interfaces:
  Comparable<BinaryComparable>, Writable, WritableComparable<BinaryComparable>

    public class Text

extends BinaryComparable
implements WritableComparable<BinaryComparable>

This class stores text using standard UTF8 encoding. It provides methods to serialize, deserialize, and compare texts at byte level. The type of length is integer and is serialized using zero-compressed format.

In addition, it provides methods for string traversal without converting the byte array to a string.

Also includes utilities for serializing/deserialing a string, coding/decoding a string, checking if a byte array contains valid UTF8 code, calculating the length of an encoded string.

Nested Class Summary
`static class` | `Text.Comparator` A WritableComparator optimized for Text keys.

Constructor Summary
`Text()`
`Text(byte[] utf8)` Construct from a byte array.
`Text(String string)` Construct from a string.
`Text(Text utf8)` Construct from another text.

Method Summary
`void` | `append(byte[] utf8, int start, int len)` Append a range of bytes to the end of the given text
`static int` | `bytesToCodePoint(ByteBuffer bytes)` Returns the next code point at the current position in the buffer.
`int` | `charAt(int position)` Returns the Unicode Scalar Value (32-bit integer value) for the character at `position`.
`void` | `clear()` Clear the string to empty.
`static String` | `decode(byte[] utf8)` Converts the provided byte array to a String using the UTF-8 encoding.
`static String` | `decode(byte[] utf8, int start, int length)`
`static String` | `decode(byte[] utf8, int start, int length, boolean replace)` Converts the provided byte array to a String using the UTF-8 encoding.
`static ByteBuffer` | `encode(String string)` Converts the provided String to bytes using the UTF-8 encoding.
`static ByteBuffer` | `encode(String string, boolean replace)` Converts the provided String to bytes using the UTF-8 encoding.
`boolean` | `equals(Object o)` Returns true iff `o` is a Text with the same contents.
`int` | `find(String what)`
`int` | `find(String what, int start)` Finds any occurence of `what` in the backing buffer, starting as position `start`.
`byte[]` | `getBytes()` Returns the raw bytes; however, only data up to `getLength()` is valid.
`int` | `getLength()` Returns the number of bytes in the byte array
`int` | `hashCode()` Return a hash of the bytes returned from {#getBytes()}.
`void` | `readFields(DataInput in)` deserialize
`static String` | `readString(DataInput in)` Read a UTF8 encoded string from in
`void` | `set(byte[] utf8)` Set to a utf8 byte array
`void` | `set(byte[] utf8, int start, int len)` Set the Text to range of bytes
`void` | `set(String string)` Set to contain the contents of a string.
`void` | `set(Text other)` copy a text.
`static void` | `skip(DataInput in)` Skips over one Text in the input.
`String` | `toString()` Convert text back to string
`static int` | `utf8Length(String string)` For the given string, returns the number of UTF-8 bytes required to encode the string.
`static void` | `validateUTF8(byte[] utf8)` Check if a byte array contains valid utf-8
`static void` | `validateUTF8(byte[] utf8, int start, int len)` Check to see if a byte array is valid utf-8
`void` | `write(DataOutput out)` serialize write this object to out length uses zero-compressed encoding
`static int` | `writeString(DataOutput out, String s)` Write a UTF8 encoded string to out

Methods inherited from class org.apache.hadoop.io.BinaryComparable
`compareTo, compareTo`

Methods inherited from class java.lang.Object
`clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

Methods inherited from interface java.lang.Comparable
`compareTo`

Constructor Detail

### Text

    public Text()

### Text

    public Text(String string)

  Construct from a string.

### Text

    public Text(Text utf8)

  Construct from another text.

### Text

    public Text(byte[] utf8)

  Construct from a byte array.

Method Detail

### getBytes

    public byte[] getBytes()

  Returns the raw bytes; however, only data up to `getLength()` is valid.

  Specified by:
    `getBytes` in class `BinaryComparable`

### getLength

    public int getLength()

  Returns the number of bytes in the byte array

  Specified by:
    `getLength` in class `BinaryComparable`

### charAt

    public int charAt(int position)

  Returns the Unicode Scalar Value (32-bit integer value) for the character at `position`. Note that this method avoids using the converter or doing String instatiation

  Returns:
    the Unicode scalar value at position or -1 if the position is invalid or points to a trailing byte

### find

    public int find(String what)

### find

    public int find(String what,
                    int start)

  Finds any occurence of `what` in the backing buffer, starting as position `start`. The starting position is measured in bytes and the return value is in terms of byte position in the buffer. The backing buffer is not converted to a string for this operation.

  Returns:
    byte position of the first occurence of the search string in the UTF-8 buffer or -1 if not found

### set

    public void set(String string)

  Set to contain the contents of a string.

### set

    public void set(byte[] utf8)

  Set to a utf8 byte array

### set

    public void set(Text other)

  copy a text.

### set

    public void set(byte[] utf8,
                    int start,
                    int len)

  Set the Text to range of bytes

  Parameters:
    `utf8` - the data to copy from
    `start` - the first position of the new string
    `len` - the number of bytes of the new string

### append

    public void append(byte[] utf8,
                       int start,
                       int len)

  Append a range of bytes to the end of the given text

  Parameters:
    `utf8` - the data to copy from
    `start` - the first position to append from utf8
    `len` - the number of bytes to append

### clear

    public void clear()

  Clear the string to empty.

### toString

    public String toString()

  Convert text back to string

  Overrides:
    `toString` in class `Object`
  See Also:
    `Object.toString()`

### readFields

    public void readFields(DataInput in)
                    throws IOException

  deserialize

  Specified by:
    `readFields` in interface `Writable`
  Parameters:
    `in` - `DataInput` to deseriablize this object from.
  Throws:
    `IOException`

### skip

    public static void skip(DataInput in)
                     throws IOException

  Skips over one Text in the input.

  Throws:
    `IOException`

### write

    public void write(DataOutput out)
               throws IOException

  serialize write this object to out length uses zero-compressed encoding

  Specified by:
    `write` in interface `Writable`
  Parameters:
    `out` - `DataOuput` to serialize this object into.
  Throws:
    `IOException`
  See Also:
    `Writable.write(DataOutput)`

### equals

    public boolean equals(Object o)

  Returns true iff `o` is a Text with the same contents.

  Overrides:
    `equals` in class `BinaryComparable`

### hashCode

    public int hashCode()

  Description copied from class: `BinaryComparable`
  Return a hash of the bytes returned from {#getBytes()}.

  Overrides:
    `hashCode` in class `BinaryComparable`
  See Also:
    `WritableComparator.hashBytes(byte[],int)`

### decode

    public static String decode(byte[] utf8)
                         throws CharacterCodingException

  Converts the provided byte array to a String using the UTF-8 encoding. If the input is malformed, replace by a default value.

  Throws:
    `CharacterCodingException`

### decode

    public static String decode(byte[] utf8,
                                int start,
                                int length)
                         throws CharacterCodingException

  Throws:
    `CharacterCodingException`

### decode

    public static String decode(byte[] utf8,
                                int start,
                                int length,
                                boolean replace)
                         throws CharacterCodingException

  Converts the provided byte array to a String using the UTF-8 encoding. If `replace` is true, then malformed input is replaced with the substitution character, which is U+FFFD. Otherwise the method throws a MalformedInputException.

  Throws:
    `CharacterCodingException`

### encode

    public static ByteBuffer encode(String string)
                             throws CharacterCodingException

  Converts the provided String to bytes using the UTF-8 encoding. If the input is malformed, invalid chars are replaced by a default value.

  Returns:
    ByteBuffer: bytes stores at ByteBuffer.array() and length is ByteBuffer.limit()
  Throws:
    `CharacterCodingException`

### encode

    public static ByteBuffer encode(String string,
                                    boolean replace)
                             throws CharacterCodingException

  Converts the provided String to bytes using the UTF-8 encoding. If `replace` is true, then malformed input is replaced with the substitution character, which is U+FFFD. Otherwise the method throws a MalformedInputException.

  Returns:
    ByteBuffer: bytes stores at ByteBuffer.array() and length is ByteBuffer.limit()
  Throws:
    `CharacterCodingException`

### readString

    public static String readString(DataInput in)
                             throws IOException

  Read a UTF8 encoded string from in

  Throws:
    `IOException`

### writeString

    public static int writeString(DataOutput out,
                                  String s)
                           throws IOException

  Write a UTF8 encoded string to out

  Throws:
    `IOException`

### validateUTF8

    public static void validateUTF8(byte[] utf8)
                             throws MalformedInputException

  Check if a byte array contains valid utf-8

  Parameters:
    `utf8` - byte array
  Throws:
    `MalformedInputException` - if the byte array contains invalid utf-8

### validateUTF8

    public static void validateUTF8(byte[] utf8,
                                    int start,
                                    int len)
                             throws MalformedInputException

  Check to see if a byte array is valid utf-8

  Parameters:
    `utf8` - the array of bytes
    `start` - the offset of the first byte in the array
    `len` - the length of the byte sequence
  Throws:
    `MalformedInputException` - if the byte array contains invalid bytes

### bytesToCodePoint

    public static int bytesToCodePoint(ByteBuffer bytes)

  Returns the next code point at the current position in the buffer. The buffer's position will be incremented. Any mark set on this buffer will be changed by this method!

### utf8Length

    public static int utf8Length(String string)

  For the given string, returns the number of UTF-8 bytes required to encode the string.

  Parameters:
    `string` - text to encode
  Returns:
    number of UTF-8 bytes required to encode

Overview | Package | Class | Use | Tree | Deprecated | Index | Help
PREV CLASS NEXT CLASS | FRAMES NO FRAMES
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD

Copyright © 2009 The Apache Software Foundation