Advanced Data Structures - Java Concepts - page 965

708

Table 1 Sample Strings and Their Hash Codes

String Hash Code

ÐAdamÑ

2035631

ÐEveÑ

70068

ÐHarryÑ

69496448

ÐJimÑ

74478

ÐJoeÑ

74656

ÐJulietÑ

Ȑ2065036585

ÐKatherineÑ

2079199209

ÐSueÑ

83491

It is possible for two or more distinct objects to have the same hash code; this is
called a collision. A good hash function minimizes collisions. For example, the
String class defines a hash function for strings that does a good job of producing
different integer values for different strings. Table 1 shows some examples of strings
and their hash codes. You will see in Section 16.4 how these values are obtained.

A good hash function minimizes collisionsȌidentical hash codes for different
objects.

Section 16.4 explains how you should redefine the hashCode method for other
classes.

A hash code is used as an array index into a hash table. In the simplest
implementation of a hash table, you could make an array and insert each object at the
location of its hash code (see Figure 5 ).