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Lecture

Equality, Order, and Hashing

In course

CS-108: Practice of object-oriented programming

Les étudiants perfectionnent leurs connaissances en Java et les mettent en pratique en réalisant un projet de taille conséquente. Ils apprennent à utiliser et à mettre en œuvre les principaux types de collections (listes, ensembles, tables associatives), e ...

Description

This lecture covers the concepts of hashing, equality, and order in Java. It explains how hashing functions work, the importance of hash codes, and the relationship between hash codes and object equality. The instructor emphasizes the need for compatibility between hashcode and equals methods to ensure correct behavior in collections. Examples and code snippets are provided to illustrate these concepts.

Instructor

Michel Schinz

Official source

Ontological neighbourhood

Theoretical computer science

Programming language theory: High-level programming languages

Related concepts (32)

Hash function

A hash function is any function that can be used to map data of arbitrary size to fixed-size values, though there are some hash functions that support variable length output. The values returned by a hash function are called hash values, hash codes, digests, or simply hashes. The values are usually used to index a fixed-size table called a hash table. Use of a hash function to index a hash table is called hashing or scatter storage addressing.

Java syntax

The syntax of Java is the set of rules defining how a Java program is written and interpreted. The syntax is mostly derived from C and C++. Unlike in C++, in Java there are no global functions or variables, but there are data members which are also regarded as global variables. All code belongs to classes and all values are objects. The only exception is the primitive types, which are not represented by a class instance for performance reasons (though can be automatically converted to objects and vice versa via autoboxing).

Hash table

In computing, a hash table, also known as hash map, is a data structure that implements an associative array or dictionary. It is an abstract data type that maps keys to values. A hash table uses a hash function to compute an index, also called a hash code, into an array of buckets or slots, from which the desired value can be found. During lookup, the key is hashed and the resulting hash indicates where the corresponding value is stored.

Java applet

Java applets were small applications written in the Java programming language, or another programming language that compiles to Java bytecode, and delivered to users in the form of Java bytecode. The user launched the Java applet from a web page, and the applet was then executed within a Java virtual machine (JVM) in a process separate from the web browser itself. A Java applet could appear in a frame of the web page, a new application window, Sun's AppletViewer, or a stand-alone tool for testing applets.

Java (programming language)

Java is a high-level, class-based, object-oriented programming language that is designed to have as few implementation dependencies as possible. It is a general-purpose programming language intended to let programmers write once, run anywhere (WORA), meaning that compiled Java code can run on all platforms that support Java without the need to recompile. Java applications are typically compiled to bytecode that can run on any Java virtual machine (JVM) regardless of the underlying computer architecture.

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