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jsdsi
Class HashOp  

java.lang.Object
  jsdsi.Obj
      jsdsi.Op
          jsdsi.HashOp

All Implemented Interfaces:

Element

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public class HashOp

extends Op

A hash operation that instructs a verifier to hash an object for later reference.

Version:

$Revision: 1.2 $ $Date: 2003/04/22 21:37:40 $

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Nested Class Summary

 

Nested classes inherited from class jsdsi.Element

Element.Default

 

Field Summary
private  java.lang.String	algo           The hash algorithm used in this hash op.

 

Constructor Summary

HashOp(java.lang.String a)           Creates a new HashOp for a given hash algorithm.

 

Method Summary
boolean	equals(java.lang.Object o)           Determine whether this Object is semantically equal to another Object.
java.lang.String	getAlgorithm()           Returns the name of the hash algorithm of this HashOp.
int	hashCode()           Get a value that represents this Object, as uniquely as possible within the confines of an int.
(package private) static HashOp	parseHashOp(java.util.Iterator obody)           Parses a HashOp where the parameters are stored in a given Iterator.
SexpList	toSexp()           Creates an SexpList-representation of this HashOp-

 

Methods inherited from class jsdsi.Op

parseOp

 

Methods inherited from class jsdsi.Obj

parseObj, toByteArray, toString

 

Methods inherited from class java.lang.Object

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

 

Field Detail

algo

private final java.lang.String algo

The hash algorithm used in this hash op.

Constructor Detail

HashOp

public HashOp(java.lang.String a)

Creates a new HashOp for a given hash algorithm.

Method Detail

getAlgorithm

public java.lang.String getAlgorithm()

Returns the name of the hash algorithm of this HashOp.

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equals

public boolean equals(java.lang.Object o)

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.

Specified by:

equals in class Obj

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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)

Specified by:

hashCode in class Obj

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toSexp

public SexpList toSexp()

Creates an SexpList-representation of this HashOp-

Specified by:

toSexp in interface Element

Specified by:

toSexp in class Obj

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parseHashOp

static HashOp parseHashOp(java.util.Iterator obody)
                   throws SexpParseException

Parses a HashOp where the parameters are stored in a given Iterator.

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