Hasher (Guava: Google Core Libraries for Java 23.5-jre API)

All Superinterfaces:

PrimitiveSink
```
@Beta
public interface Hasher
extends PrimitiveSink
```
A PrimitiveSink that can compute a hash code after reading the input. Each hasher should translate all multibyte values (putInt(int), putLong(long), etc) to bytes in little-endian order.
Warning: The result of calling any methods after calling hash() is undefined.
Warning: Using a specific character encoding when hashing a CharSequence with putString(CharSequence, Charset) is generally only useful for cross-language compatibility (otherwise prefer putUnencodedChars(java.lang.CharSequence)). However, the character encodings must be identical across languages. Also beware that Charset definitions may occasionally change between Java releases.
Warning: Chunks of data that are put into the Hasher are not delimited. The resulting HashCode is dependent only on the bytes inserted, and the order in which they were inserted, not how those bytes were chunked into discrete put() operations. For example, the following three expressions all generate colliding hash codes:
```
   

   newHasher().putByte(b1).putByte(b2).putByte(b3).hash()
   newHasher().putByte(b1).putBytes(new byte[] { b2, b3 }).hash()
   newHasher().putBytes(new byte[] { b1, b2, b3 }).hash()
```
If you wish to avoid this, you should either prepend or append the size of each chunk. Keep in mind that when dealing with char sequences, the encoded form of two concatenated char sequences is not equivalent to the concatenation of their encoded form. Therefore, putString(CharSequence, Charset) should only be used consistently with complete sequences and not broken into chunks.
Since:

11.0

Author:

Kevin Bourrillion

Method Summary

All Methods Instance Methods Abstract Methods Deprecated Methods
Modifier and Type	Method and Description
`HashCode`	`hash()` Computes a hash code based on the data that have been provided to this hasher.
`int`	`hashCode()` Deprecated. This returns `Object.hashCode()`; you almost certainly mean to call `hash().asInt()`.
`Hasher`	`putBoolean(boolean b)` Equivalent to `putByte(b ? (byte) 1 : (byte) 0)`.
`Hasher`	`putByte(byte b)` Puts a byte into this sink.
`Hasher`	`putBytes(byte[] bytes)` Puts an array of bytes into this sink.
`Hasher`	`putBytes(byte[] bytes, int off, int len)` Puts a chunk of an array of bytes into this sink.
`Hasher`	`putBytes(ByteBuffer bytes)` Puts the remaining bytes of a byte buffer into this sink.
`Hasher`	`putChar(char c)` Puts a character into this sink.
`Hasher`	`putDouble(double d)` Equivalent to `putLong(Double.doubleToRawLongBits(d))`.
`Hasher`	`putFloat(float f)` Equivalent to `putInt(Float.floatToRawIntBits(f))`.
`Hasher`	`putInt(int i)` Puts an int into this sink.
`Hasher`	`putLong(long l)` Puts a long into this sink.
`<T> Hasher`	`putObject(T instance, Funnel<? super T> funnel)` A simple convenience for `funnel.funnel(object, this)`.
`Hasher`	`putShort(short s)` Puts a short into this sink.
`Hasher`	`putString(CharSequence charSequence, Charset charset)` Equivalent to `putBytes(charSequence.toString().getBytes(charset))`.
`Hasher`	`putUnencodedChars(CharSequence charSequence)` Equivalent to processing each `char` value in the `CharSequence`, in order.

- Method Detail
  - putByte
```
Hasher putByte(byte b)
```
    Description copied from interface: PrimitiveSink
    
    Puts a byte into this sink.
    
    Specified by:
    
    putByte in interface PrimitiveSink
    
    Parameters:
    
    b - a byte
    
    Returns:
    
    this instance
  - putBytes
```
Hasher putBytes(byte[] bytes)
```
    Description copied from interface: PrimitiveSink
    
    Puts an array of bytes into this sink.
    
    Specified by:
    
    putBytes in interface PrimitiveSink
    
    Parameters:
    
    bytes - a byte array
    
    Returns:
    
    this instance
  - putBytes
```
Hasher putBytes(byte[] bytes,
                int off,
                int len)
```
    Description copied from interface: PrimitiveSink
    
    Puts a chunk of an array of bytes into this sink. bytes[off] is the first byte written, bytes[off + len - 1] is the last.
    
    Specified by:
    
    putBytes in interface PrimitiveSink
    
    Parameters:
    
    bytes - a byte array
    
    off - the start offset in the array
    
    len - the number of bytes to write
    
    Returns:
    
    this instance
  - putBytes
```
Hasher putBytes(ByteBuffer bytes)
```
    Description copied from interface: PrimitiveSink
    
    Puts the remaining bytes of a byte buffer into this sink. bytes.position() is the first byte written, bytes.limit() - 1 is the last. The position of the buffer will be equal to the limit when this method returns.
    
    Specified by:
    
    putBytes in interface PrimitiveSink
    
    Parameters:
    
    bytes - a byte buffer
    
    Returns:
    
    this instance
  - putShort
```
Hasher putShort(short s)
```
    Description copied from interface: PrimitiveSink
    
    Puts a short into this sink.
    
    Specified by:
    
    putShort in interface PrimitiveSink
  - putInt
```
Hasher putInt(int i)
```
    Description copied from interface: PrimitiveSink
    
    Puts an int into this sink.
    
    Specified by:
    
    putInt in interface PrimitiveSink
  - putLong
```
Hasher putLong(long l)
```
    Description copied from interface: PrimitiveSink
    
    Puts a long into this sink.
    
    Specified by:
    
    putLong in interface PrimitiveSink
  - putFloat
```
Hasher putFloat(float f)
```
    Equivalent to putInt(Float.floatToRawIntBits(f)).
    
    Specified by:
    
    putFloat in interface PrimitiveSink
  - putDouble
```
Hasher putDouble(double d)
```
    Equivalent to putLong(Double.doubleToRawLongBits(d)).
    
    Specified by:
    
    putDouble in interface PrimitiveSink
  - putBoolean
```
Hasher putBoolean(boolean b)
```
    Equivalent to putByte(b ? (byte) 1 : (byte) 0).
    
    Specified by:
    
    putBoolean in interface PrimitiveSink
  - putChar
```
Hasher putChar(char c)
```
    Description copied from interface: PrimitiveSink
    
    Puts a character into this sink.
    
    Specified by:
    
    putChar in interface PrimitiveSink
  - putUnencodedChars
```
Hasher putUnencodedChars(CharSequence charSequence)
```
    Equivalent to processing each char value in the CharSequence, in order. In other words, no character encoding is performed; the low byte and high byte of each char are hashed directly (in that order). The input must not be updated while this method is in progress.
    Warning: This method will produce different output than most other languages do when running the same hash function on the equivalent input. For cross-language compatibility, use putString(java.lang.CharSequence, java.nio.charset.Charset), usually with a charset of UTF-8. For other use cases, use putUnencodedChars.
    
    Specified by:
    
    putUnencodedChars in interface PrimitiveSink
    
    Since:
    
    15.0 (since 11.0 as putString(CharSequence)).
  - putString
```
Hasher putString(CharSequence charSequence,
                 Charset charset)
```
    Equivalent to putBytes(charSequence.toString().getBytes(charset)).
    Warning: This method, which reencodes the input before hashing it, is useful only for cross-language compatibility. For other use cases, prefer putUnencodedChars(java.lang.CharSequence), which is faster, produces the same output across Java releases, and hashes every char in the input, even if some are invalid.
    
    Specified by:
    
    putString in interface PrimitiveSink
  - putObject
```
<T> Hasher putObject(T instance,
                     Funnel<? super T> funnel)
```
    A simple convenience for funnel.funnel(object, this).
  - hash
```
HashCode hash()
```
    Computes a hash code based on the data that have been provided to this hasher. The result is unspecified if this method is called more than once on the same instance.
  - hashCode
```
@Deprecated
int hashCode()
```
    Deprecated. This returns Object.hashCode(); you almost certainly mean to call hash().asInt().
    Returns a hash code value for the object. This method is supported for the benefit of hash tables such as those provided by HashMap.
    The general contract of hashCode is:
    - Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application.
    - If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.
    - It is not required that if two objects are unequal according to the Object.equals(java.lang.Object) method, then calling the hashCode method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hash tables.
    As much as is reasonably practical, the hashCode method defined by class Object does return distinct integers for distinct objects. (This is typically implemented by converting the internal address of the object into an integer, but this implementation technique is not required by the Java™ programming language.)
    Overrides:
    
    hashCode in class Object
    
    Returns:
    
    a hash code value for this object.
    
    See Also:
    
    Object.equals(java.lang.Object), System.identityHashCode(java.lang.Object)

Interface Hasher

Method Summary

Method Detail

putByte

putBytes

putBytes

putBytes

putShort

putInt

putLong

putFloat

putDouble

putBoolean

putChar

putUnencodedChars

putString

putObject

hash

hashCode