HashCodeGenerator (ph-commons 9.4.1 API)

java.lang.Object
- com.helger.commons.hashcode.HashCodeGenerator

All Implemented Interfaces:

IHashCodeGenerator, IAppendable<IHashCodeGenerator>
```
@NotThreadSafe
public final class HashCodeGenerator
extends Object
implements IHashCodeGenerator
```
A small hash code creation class based on the article found in the net. See this article for details.
After calling append(Object) for all objects use getHashCode() to retrieve the calculated hash code. Once the hash code was calculated no modifications are allowed.

A real world example for a final class derived from Object or a base class looks like this:
```
 @Override
 public int hashCode ()
 {
   return new HashCodeGenerator (this).append (member1).append (member2).getHashCode ();
 }
 
```
For a derived class, the typical code looks like this, assuming the base class also uses HashCodeGenerator:
```
 @Override
 public int hashCode ()
 {
   return HashCodeGenerator.getDerived (super.hashCode ()).append (member3).append (member4).getHashCode ();
 }
 
```
Author:

Philip Helger

Field Summary

Fields
Modifier and Type Field and Description

static int INITIAL_HASHCODE
Use a prime number as the start.
- Fields inherited from interface com.helger.commons.hashcode.IHashCodeGenerator
  ILLEGAL_HASHCODE

Fields
Modifier and Type	Field and Description
`static int`	`INITIAL_HASHCODE` Use a prime number as the start.

Constructor Summary

Constructors
Constructor and Description
`HashCodeGenerator(Class<?> aClass)` This constructor requires a class name, because in case a class has no instance variables the hash code may be the same for different instances of different classes.
`HashCodeGenerator(Object aSrcObject)` This is a sanity constructor that allows for any object to be passed in the constructor (e.g.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods Deprecated Methods
Modifier and Type	Method and Description
`HashCodeGenerator`	`append(boolean x)` Atomic type hash code generation.
`HashCodeGenerator`	`append(boolean[] x)` Array hash code generation.
`HashCodeGenerator`	`append(byte x)` Atomic type hash code generation.
`HashCodeGenerator`	`append(byte[] x)` Array hash code generation.
`HashCodeGenerator`	`append(char x)` Atomic type hash code generation.
`HashCodeGenerator`	`append(char[] x)` Array hash code generation.
`HashCodeGenerator`	`append(double x)` Atomic type hash code generation.
`HashCodeGenerator`	`append(double[] x)` Array hash code generation.
`HashCodeGenerator`	`append(Enum<?> x)` Object hash code generation.
`HashCodeGenerator`	`append(Enum<?>[] x)` Array hash code generation.
`HashCodeGenerator`	`append(float x)` Atomic type hash code generation.
`HashCodeGenerator`	`append(float[] x)` Array hash code generation.
`HashCodeGenerator`	`append(int x)` Atomic type hash code generation.
`HashCodeGenerator`	`append(int[] x)` Array hash code generation.
`HashCodeGenerator`	`append(Iterable<?> x)`
`HashCodeGenerator`	`append(long x)` Atomic type hash code generation.
`HashCodeGenerator`	`append(long[] x)` Array hash code generation.
`HashCodeGenerator`	`append(Map<?,?> x)`
`HashCodeGenerator`	`append(Node x)`
`HashCodeGenerator`	`append(Object x)` Object hash code generation.
`HashCodeGenerator`	`append(Object[] x)` Array hash code generation.
`HashCodeGenerator`	`append(short x)` Atomic type hash code generation.
`HashCodeGenerator`	`append(short[] x)` Array hash code generation.
`HashCodeGenerator`	`append(StringBuffer x)` Type specific hash code generation because parameter class has no overloaded equals method.
`HashCodeGenerator`	`append(StringBuilder x)` Type specific hash code generation because parameter class has no overloaded equals method.
`boolean`	`equals(Object o)` Deprecated. Don't call this
`static HashCodeGenerator`	`getDerived(int nSuperHashCode)` Create a `HashCodeGenerator` for derived classes where the base class also uses the `HashCodeGenerator`.
`int`	`getHashCode()` Retrieve the final hash code.
`int`	`hashCode()` Deprecated. Don't call this
`boolean`	`isClosed()`

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

- Field Detail
  - INITIAL_HASHCODE
```
public static final int INITIAL_HASHCODE
```
    Use a prime number as the start.
    
    See Also:
    
    Constant Field Values
- Constructor Detail
  - HashCodeGenerator
```
public HashCodeGenerator(@Nonnull
                         Object aSrcObject)
```
    This is a sanity constructor that allows for any object to be passed in the constructor (e.g. this) from which the class is extracted as the initial value of the hash code.
    
    Parameters:
    
    aSrcObject - The source object from which the class is extracted. May not be null.
  - HashCodeGenerator
```
public HashCodeGenerator(@Nonnull
                         Class<?> aClass)
```
    This constructor requires a class name, because in case a class has no instance variables the hash code may be the same for different instances of different classes.
    
    Parameters:
    
    aClass - The class this instance is about to create a hash code for. May not be null.
- Method Detail
  - isClosed
```
public boolean isClosed()
```
  - append
```
@Nonnull
public HashCodeGenerator append(boolean x)
```
    Atomic type hash code generation.
    
    Specified by:
    
    append in interface IAppendable<IHashCodeGenerator>
    
    Parameters:
    
    x - Array to add
    
    Returns:
    
    this
  - append
```
@Nonnull
public HashCodeGenerator append(byte x)
```
    Atomic type hash code generation.
    
    Specified by:
    
    append in interface IAppendable<IHashCodeGenerator>
    
    Parameters:
    
    x - Array to add
    
    Returns:
    
    this
  - append
```
@Nonnull
public HashCodeGenerator append(char x)
```
    Atomic type hash code generation.
    
    Specified by:
    
    append in interface IAppendable<IHashCodeGenerator>
    
    Parameters:
    
    x - Array to add
    
    Returns:
    
    this
  - append
```
@Nonnull
public HashCodeGenerator append(double x)
```
    Atomic type hash code generation.
    
    Specified by:
    
    append in interface IAppendable<IHashCodeGenerator>
    
    Parameters:
    
    x - Array to add
    
    Returns:
    
    this
  - append
```
@Nonnull
public HashCodeGenerator append(float x)
```
    Atomic type hash code generation.
    
    Specified by:
    
    append in interface IAppendable<IHashCodeGenerator>
    
    Parameters:
    
    x - Array to add
    
    Returns:
    
    this
  - append
```
@Nonnull
public HashCodeGenerator append(int x)
```
    Atomic type hash code generation.
    
    Specified by:
    
    append in interface IAppendable<IHashCodeGenerator>
    
    Parameters:
    
    x - Array to add
    
    Returns:
    
    this
  - append
```
@Nonnull
public HashCodeGenerator append(long x)
```
    Atomic type hash code generation.
    
    Specified by:
    
    append in interface IAppendable<IHashCodeGenerator>
    
    Parameters:
    
    x - Array to add
    
    Returns:
    
    this
  - append
```
@Nonnull
public HashCodeGenerator append(short x)
```
    Atomic type hash code generation.
    
    Specified by:
    
    append in interface IAppendable<IHashCodeGenerator>
    
    Parameters:
    
    x - Array to add
    
    Returns:
    
    this
  - append
```
@Nonnull
public HashCodeGenerator append(@Nullable
                                          Object x)
```
    Object hash code generation.
    
    Specified by:
    
    append in interface IAppendable<IHashCodeGenerator>
    
    Parameters:
    
    x - Array to add
    
    Returns:
    
    this
  - append
```
@Nonnull
public HashCodeGenerator append(@Nullable
                                          Enum<?> x)
```
    Object hash code generation.
    
    Specified by:
    
    append in interface IAppendable<IHashCodeGenerator>
    
    Parameters:
    
    x - Array to add
    
    Returns:
    
    this
  - append
```
@Nonnull
public HashCodeGenerator append(@Nullable
                                          boolean[] x)
```
    Array hash code generation.
    
    Specified by:
    
    append in interface IAppendable<IHashCodeGenerator>
    
    Parameters:
    
    x - Array to add
    
    Returns:
    
    this
  - append
```
@Nonnull
public HashCodeGenerator append(@Nullable
                                          byte[] x)
```
    Array hash code generation.
    
    Specified by:
    
    append in interface IAppendable<IHashCodeGenerator>
    
    Parameters:
    
    x - Array to add
    
    Returns:
    
    this
  - append
```
@Nonnull
public HashCodeGenerator append(@Nullable
                                          char[] x)
```
    Array hash code generation.
    
    Specified by:
    
    append in interface IAppendable<IHashCodeGenerator>
    
    Parameters:
    
    x - Array to add
    
    Returns:
    
    this
  - append
```
@Nonnull
public HashCodeGenerator append(@Nullable
                                          double[] x)
```
    Array hash code generation.
    
    Specified by:
    
    append in interface IAppendable<IHashCodeGenerator>
    
    Parameters:
    
    x - Array to add
    
    Returns:
    
    this
  - append
```
@Nonnull
public HashCodeGenerator append(@Nullable
                                          float[] x)
```
    Array hash code generation.
    
    Specified by:
    
    append in interface IAppendable<IHashCodeGenerator>
    
    Parameters:
    
    x - Array to add
    
    Returns:
    
    this
  - append
```
@Nonnull
public HashCodeGenerator append(@Nullable
                                          int[] x)
```
    Array hash code generation.
    
    Specified by:
    
    append in interface IAppendable<IHashCodeGenerator>
    
    Parameters:
    
    x - Array to add
    
    Returns:
    
    this
  - append
```
@Nonnull
public HashCodeGenerator append(@Nullable
                                          long[] x)
```
    Array hash code generation.
    
    Specified by:
    
    append in interface IAppendable<IHashCodeGenerator>
    
    Parameters:
    
    x - Array to add
    
    Returns:
    
    this
  - append
```
@Nonnull
public HashCodeGenerator append(@Nullable
                                          short[] x)
```
    Array hash code generation.
    
    Specified by:
    
    append in interface IAppendable<IHashCodeGenerator>
    
    Parameters:
    
    x - Array to add
    
    Returns:
    
    this
  - append
```
@Nonnull
public HashCodeGenerator append(@Nullable
                                          Object[] x)
```
    Array hash code generation.
    
    Specified by:
    
    append in interface IAppendable<IHashCodeGenerator>
    
    Parameters:
    
    x - Array to add
    
    Returns:
    
    this
  - append
```
@Nonnull
public HashCodeGenerator append(@Nullable
                                          Enum<?>[] x)
```
    Array hash code generation.
    
    Specified by:
    
    append in interface IAppendable<IHashCodeGenerator>
    
    Parameters:
    
    x - Array to add
    
    Returns:
    
    this
  - append
```
@Nonnull
public HashCodeGenerator append(@Nullable
                                          StringBuffer x)
```
    Type specific hash code generation because parameter class has no overloaded equals method.
    
    Parameters:
    
    x - object to add
    
    Returns:
    
    this
  - append
```
@Nonnull
public HashCodeGenerator append(@Nullable
                                          StringBuilder x)
```
    Type specific hash code generation because parameter class has no overloaded equals method.
    
    Parameters:
    
    x - object to add
    
    Returns:
    
    this
  - append
```
@Nonnull
public HashCodeGenerator append(@Nullable
                                          Iterable<?> x)
```
    Specified by:
    
    append in interface IAppendable<IHashCodeGenerator>
    
    Parameters:
    
    x - to be included in the hash code generation.
    
    Returns:
    
    this
  - append
```
@Nonnull
public HashCodeGenerator append(@Nullable
                                          Map<?,?> x)
```
    Specified by:
    
    append in interface IAppendable<IHashCodeGenerator>
    
    Parameters:
    
    x - to be included in the hash code generation.
    
    Returns:
    
    this
  - append
```
@Nonnull
public HashCodeGenerator append(@Nullable
                                          Node x)
```
    Specified by:
    
    append in interface IAppendable<IHashCodeGenerator>
    
    Parameters:
    
    x - to be included in the hash code generation.
    
    Returns:
    
    this
  - getHashCode
```
public int getHashCode()
```
    Retrieve the final hash code. Once this method has been called, no further calls to append can be done since the hash value is locked!
    
    Specified by:
    
    getHashCode in interface IHashCodeGenerator
    
    Returns:
    
    The finally completed hash code. The returned value is never IHashCodeGenerator.ILLEGAL_HASHCODE. If the calculated hash code would be IHashCodeGenerator.ILLEGAL_HASHCODE it is changed to -1 instead.
  - equals
```
@Deprecated
public boolean equals(Object o)
```
    Deprecated. Don't call this
    
    Never compare HashCodeGenerator objects :)
    
    Overrides:
    
    equals in class Object
  - hashCode
```
@Deprecated
public int hashCode()
```
    Deprecated. Don't call this
    
    Always use getHashCode()
    
    Overrides:
    
    hashCode in class Object
    
    Returns:
    
    getHashCode()
    
    See Also:
    
    getHashCode()
  - getDerived
```
@Nonnull
public static HashCodeGenerator getDerived(int nSuperHashCode)
```
    Create a HashCodeGenerator for derived classes where the base class also uses the HashCodeGenerator. This avoid calculating the hash code of the class name more than once.
    
    Parameters:
    
    nSuperHashCode - Always pass in super.hashCode ()
    
    Returns:
    
    Never null

Class HashCodeGenerator

Field Summary

Fields inherited from interface com.helger.commons.hashcode.IHashCodeGenerator

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

INITIAL_HASHCODE

Constructor Detail

HashCodeGenerator

HashCodeGenerator

Method Detail

isClosed

append

append

append

append

append

append

append

append

append

append

append

append

append

append

append

append

append

append

append

append

append

append

append

append

append

getHashCode

equals

hashCode

getDerived