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org.apache.derby.iapi.store.raw
Class PageKey  

java.lang.Object
  org.apache.derby.iapi.store.raw.PageKey

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public class PageKey

extends java.lang.Object

A key that identifies a BasePage. Used as the key for the caching mechanism.
MT - Immutable :

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Field Summary
private  ContainerKey	container
private  long	pageNumber

 

Constructor Summary

PageKey(ContainerKey key, long pageNumber)

 

Method Summary
boolean	equals(java.lang.Object other)           Determine whether this Object is semantically equal to another Object.
ContainerKey	getContainerId()
long	getPageNumber()
int	hashCode()           Get a value that represents this Object, as uniquely as possible within the confines of an int.
static PageKey	read(java.io.ObjectInput in)
java.lang.String	toString()           Convert this Object to a human-readable String.
void	writeExternal(java.io.ObjectOutput out)

 

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

 

Field Detail

container

private final ContainerKey container

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pageNumber

private final long pageNumber

Constructor Detail

PageKey

public PageKey(ContainerKey key,
               long pageNumber)

Method Detail

getPageNumber

public long getPageNumber()

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getContainerId

public ContainerKey getContainerId()

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writeExternal

public void writeExternal(java.io.ObjectOutput out)
                   throws java.io.IOException

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read

public static PageKey read(java.io.ObjectInput in)
                    throws java.io.IOException

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equals

public boolean equals(java.lang.Object other)

Description copied from class: java.lang.Object

Determine whether this Object is semantically equal to another Object.

There are some fairly strict requirements on this method which subclasses must follow:

• It must be transitive. If a.equals(b) and b.equals(c), then a.equals(c) must be true as well.
• It must be symmetric. a.equals(b) and b.equals(a) must have the same value.
• It must be reflexive. a.equals(a) must always be true.
• It must be consistent. Whichever value a.equals(b) returns on the first invocation must be the value returned on all later invocations.
• a.equals(null) must be false.
• It must be consistent with hashCode(). That is, a.equals(b) must imply a.hashCode() == b.hashCode(). The reverse is not true; two objects that are not equal may have the same hashcode, but that has the potential to harm hashing performance.

This is typically overridden to throw a java.lang.ClassCastException if the argument is not comparable to the class performing the comparison, but that is not a requirement. It is legal for a.equals(b) to be true even though a.getClass() != b.getClass(). Also, it is typical to never cause a java.lang.NullPointerException.

In general, the Collections API (java.util) use the equals method rather than the == operator to compare objects. However, java.util.IdentityHashMap is an exception to this rule, for its own good reasons.

The default implementation returns this == o.

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hashCode

public int hashCode()

Description copied from class: java.lang.Object

Get a value that represents this Object, as uniquely as possible within the confines of an int.

There are some requirements on this method which subclasses must follow:

• Semantic equality implies identical hashcodes. In other words, if a.equals(b) is true, then a.hashCode() == b.hashCode() must be as well. However, the reverse is not necessarily true, and two objects may have the same hashcode without being equal.
• It must be consistent. Whichever value o.hashCode() returns on the first invocation must be the value returned on all later invocations as long as the object exists. Notice, however, that the result of hashCode may change between separate executions of a Virtual Machine, because it is not invoked on the same object.

Notice that since hashCode is used in java.util.Hashtable and other hashing classes, a poor implementation will degrade the performance of hashing (so don't blindly implement it as returning a constant!). Also, if calculating the hash is time-consuming, a class may consider caching the results.

The default implementation returns System.identityHashCode(this)

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toString

public java.lang.String toString()

Description copied from class: java.lang.Object

Convert this Object to a human-readable String. There are no limits placed on how long this String should be or what it should contain. We suggest you make it as intuitive as possible to be able to place it into System.out.println() 55 and such.

It is typical, but not required, to ensure that this method never completes abruptly with a java.lang.RuntimeException.

This method will be called when performing string concatenation with this object. If the result is null, string concatenation will instead use "null".

The default implementation returns getClass().getName() + "@" + Integer.toHexString(hashCode()).

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Overview  Package   Class  Use  Deprecated  Index
Home >> All >> org >> apache >> derby >> iapi >> store >> [ raw overview ]	PREV CLASS  NEXT CLASS
SUMMARY:  JAVADOC |  SOURCE |  DOWNLOAD | NESTED | FIELD | CONSTR | METHOD	DETAIL: FIELD | CONSTR | METHOD

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