Apache Derby Database Engine and Embedded JDBC Driver 10.17.1.0 · org.apache.derby.iapi.store.access.KeyHasher

Modifier and Type	Field and Description
private final Object[]	objects

Access	Constructor and Description
public	KeyHasher(int size)

Modifier and Type	Method and Description
public static Object	Returns: The object to hash on. buildHashKey(Object[] The array of objects to consider objects, int[] The indexes of the objects in the hash key. indexes) Static method to return the object to hash on.
public boolean	equals(Object the reference object with which to compare. obj) Overrides java.lang.Object.equals. Indicates whether some other object is "equal to" this one.
public Object	Returns: The object stored in the array element. getObject(int The specified index. index) Get the object stored at the specified index.
public int	hashCode() Overrides java.lang.Object.hashCode. Returns a hash code value for this object.
public void	setObject(int The specified index index, Object The specified object. object) Set array element at the specified index to the specified object.

objects	back to summary
private final Object[] objects

KeyHasher	back to summary
public KeyHasher(int size)

Method Detail

buildHashKey	back to summary
public static Object buildHashKey(Object[] objects, int[] indexes) Static method to return the object to hash on. (Object stored in specifed array, if only a single object, otherwise a KeyHasher wrapping the objects to hash on. (NOTE: We optimize for in-memory hash tables, hence we only create a wrapper when needed.) Parameters objects:Object[] The array of objects to consider indexes:int[] The indexes of the objects in the hash key. Returns:Object The object to hash on.

buildHashKey

public static Object buildHashKey(Object[] objects, int[] indexes)

Static method to return the object to hash on. (Object stored in specifed array, if only a single object, otherwise a KeyHasher wrapping the objects to hash on. (NOTE: We optimize for in-memory hash tables, hence we only create a wrapper when needed.)

Parameters

objects:Object[]: The array of objects to consider
indexes:int[]: The indexes of the objects in the hash key.

Returns:Object

The object to hash on.

equals back to summary

equals	back to summary
public boolean equals(Object obj) Overrides java.lang.Object.equals. Doc from java.lang.Object.equals. Indicates whether some other object is "equal to" this one. The `equals` method implements an equivalence relation on non-null object references: It is reflexive: for any non-null reference value `x`, `x.equals(x)` should return `true`. It is symmetric: for any non-null reference values `x` and `y`, `x.equals(y)` should return `true` if and only if `y.equals(x)` returns `true`. It is transitive: for any non-null reference values `x`, `y`, and `z`, if `x.equals(y)` returns `true` and `y.equals(z)` returns `true`, then `x.equals(z)` should return `true`. It is consistent: for any non-null reference values `x` and `y`, multiple invocations of `x.equals(y)` consistently return `true` or consistently return `false`, provided no information used in `equals` comparisons on the objects is modified. For any non-null reference value `x`, `x.equals(null)` should return `false`. An equivalence relation partitions the elements it operates on into equivalence classes; all the members of an equivalence class are equal to each other. Members of an equivalence class are substitutable for each other, at least for some purposes. Parameters obj:Object the reference object with which to compare. Returns:boolean `true` if this object is the same as the obj argument; `false` otherwise.

public boolean equals(Object obj)

Overrides java.lang.Object.equals.

Doc from java.lang.Object.equals.

Indicates whether some other object is "equal to" this one.

The equals method implements an equivalence relation on non-null object references:

It is reflexive: for any non-null reference value x, x.equals(x) should return true.
It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true.
It is transitive: for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true.
It is consistent: for any non-null reference values x and y, multiple invocations of x.equals(y) consistently return true or consistently return false, provided no information used in equals comparisons on the objects is modified.
For any non-null reference value x, x.equals(null) should return false.

An equivalence relation partitions the elements it operates on into equivalence classes; all the members of an equivalence class are equal to each other. Members of an equivalence class are substitutable for each other, at least for some purposes.

Parameters

obj:Object: the reference object with which to compare.

Returns:boolean

true if this object is the same as the obj argument; false otherwise.

getObject	back to summary
public Object getObject(int index) Get the object stored at the specified index. Parameters index:int The specified index. Returns:Object The object stored in the array element.

getObject

back to summary

public Object getObject(int index)

Get the object stored at the specified index.

Parameters

index:int: The specified index.

Returns:Object

The object stored in the array element.

hashCode back to summary

hashCode	back to summary
public int hashCode() Overrides java.lang.Object.hashCode. Doc from java.lang.Object.hashCode. Returns a hash code value for this object. This method is supported for the benefit of hash tables such as those provided by `java.util.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` 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 `equals` 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. Returns:int a hash code value for this object

public int hashCode()

Overrides java.lang.Object.hashCode.

Doc from java.lang.Object.hashCode.

Returns a hash code value for this object. This method is supported for the benefit of hash tables such as those provided by java.util.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 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 equals 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.

Returns:int: a hash code value for this object

setObject	back to summary
public void setObject(int index, Object object) Set array element at the specified index to the specified object. Parameters index:int The specified index object:Object The specified object.

setObject

back to summary

public void setObject(int index, Object object)

Set array element at the specified index to the specified object.

Parameters

index:int: The specified index
object:Object: The specified object.

public Class KeyHasher

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