Tutoriais - Programação Orientada a ObjetosQuando uma abstração pode ter uma entre várias implementações possíveis, a maneira usual de acomodá-las é usando a herança. Uma classe abstrata define a interface para a abstração, e subclasses concretas a implementam de formas diferentes. Mas essa abordagem nem sempre é suficientemente flexível. A herança liga uma implementação à abstração permanentemente, o que torna difícil modificar, aumentar e reutilizar abstrações e implementações independentemente.
Empregando o padrão de projeto Bridge, desenvolva um sistema estatístico que permita ao usuário selecionar o método a ser utilizado para o calculo da média de uma série de números, que podem ser fornecidos pelo usuário por meio de um vetor, uma matriz, uma lista dentre diversas outras formas.
/*************************************************************************
* Copyright (C) 2009/2025 - Cristiano Lehrer (cristiano@ybadoo.com.br) *
* Ybadoo - Solucoes em Software Livre (ybadoo.com.br) *
* *
* Permission is granted to copy, distribute and/or modify this document *
* under the terms of the GNU Free Documentation License, Version 1.3 or *
* any later version published by the Free Software Foundation; with no *
* Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A *
* A copy of the license is included in the section entitled "GNU Free *
* Documentation License". *
* *
* Ubuntu 16.10 (GNU/Linux 4.8.0-39-generic) *
* OpenJDK Version "1.8.0_121" *
* OpenJDK 64-Bit Server VM (build 25.121-b13, mixed mode) *
*************************************************************************/
package com.ybadoo.tutoriais.poo.tutorial09.exercicio26;
/**
* Interface para a realizacao da media sobre um conjunto de elementos
*
* Implementor define a interface para as classes de implementacao. Esta
* interface nao precisa corresponder exatamente a interface de Abstraction;
* de fato, as duas interfaces podem ser bem diferentes. A interface de
* Implementor fornece somente operacoes primitivas e Abstraction define
* operacoes de nivel mais alto baseadas nestas primitivas (Gamma, 2000)
*/
public interface Mean
{
/**
* Realizar a media dos elementos
*
* @param values elementos
* @return media dos elementos
*/
public double average(Object[] values);
}/*************************************************************************
* Copyright (C) 2009/2025 - Cristiano Lehrer (cristiano@ybadoo.com.br) *
* Ybadoo - Solucoes em Software Livre (ybadoo.com.br) *
* *
* Permission is granted to copy, distribute and/or modify this document *
* under the terms of the GNU Free Documentation License, Version 1.3 or *
* any later version published by the Free Software Foundation; with no *
* Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A *
* A copy of the license is included in the section entitled "GNU Free *
* Documentation License". *
* *
* Ubuntu 16.10 (GNU/Linux 4.8.0-39-generic) *
* OpenJDK Version "1.8.0_121" *
* OpenJDK 64-Bit Server VM (build 25.121-b13, mixed mode) *
*************************************************************************/
package com.ybadoo.tutoriais.poo.tutorial09.exercicio26;
/**
* Realizar a media aritmetica
*
* ConcreteImplementor implementa a interface de Implementor e define sua
* implementacao concreta (Gamma, 2000)
*/
public class ArithmeticMean implements Mean
{
/* (non-Javadoc)
* @see com.ybadoo.tutoriais.poo.tutorial09.exercicio26.Mean#calculate(java.lang.Object[])
*/
@Override
public double average(Object[] values)
{
double sum = 0.0;
int count = 0;
for(Object value : values)
{
if(value instanceof Number)
{
sum = sum + ((Number) value).doubleValue();
count = count + 1;
}
}
return sum / count;
}
}/*************************************************************************
* Copyright (C) 2009/2025 - Cristiano Lehrer (cristiano@ybadoo.com.br) *
* Ybadoo - Solucoes em Software Livre (ybadoo.com.br) *
* *
* Permission is granted to copy, distribute and/or modify this document *
* under the terms of the GNU Free Documentation License, Version 1.3 or *
* any later version published by the Free Software Foundation; with no *
* Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A *
* A copy of the license is included in the section entitled "GNU Free *
* Documentation License". *
* *
* Ubuntu 16.10 (GNU/Linux 4.8.0-39-generic) *
* OpenJDK Version "1.8.0_121" *
* OpenJDK 64-Bit Server VM (build 25.121-b13, mixed mode) *
*************************************************************************/
package com.ybadoo.tutoriais.poo.tutorial09.exercicio26;
/**
* Realizar a media geometrica
*
* ConcreteImplementor implementa a interface de Implementor e define sua
* implementacao concreta (Gamma, 2000)
*/
public class GeometricMean implements Mean
{
/* (non-Javadoc)
* @see com.ybadoo.tutoriais.poo.tutorial09.exercicio26.Mean#calculate(java.lang.Object[])
*/
@Override
public double average(Object[] values)
{
int amount = 0;
double product = 1.0;
for(Object value : values)
{
if(value instanceof Number)
{
amount = amount + 1;
product = product * ((Number) value).doubleValue();
}
}
return Math.pow(product, 1.0/amount);
}
}/*************************************************************************
* Copyright (C) 2009/2025 - Cristiano Lehrer (cristiano@ybadoo.com.br) *
* Ybadoo - Solucoes em Software Livre (ybadoo.com.br) *
* *
* Permission is granted to copy, distribute and/or modify this document *
* under the terms of the GNU Free Documentation License, Version 1.3 or *
* any later version published by the Free Software Foundation; with no *
* Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A *
* A copy of the license is included in the section entitled "GNU Free *
* Documentation License". *
* *
* Ubuntu 16.10 (GNU/Linux 4.8.0-39-generic) *
* OpenJDK Version "1.8.0_121" *
* OpenJDK 64-Bit Server VM (build 25.121-b13, mixed mode) *
*************************************************************************/
package com.ybadoo.tutoriais.poo.tutorial09.exercicio26;
/**
* Realizar a media harmonica
*
* ConcreteImplementor implementa a interface de Implementor e define sua
* implementacao concreta (Gamma, 2000)
*/
public class HarmonicMean implements Mean
{
/* (non-Javadoc)
* @see com.ybadoo.tutoriais.poo.tutorial09.exercicio26.Mean#calculate(java.lang.Object[])
*/
@Override
public double average(Object[] values)
{
int amount = 0;
double sum = 0.0;
for(Object value : values)
{
if(value instanceof Number)
{
amount = amount + 1;
sum = sum + 1.0/((Number) value).doubleValue();;
}
}
return amount / sum;
}
}/*************************************************************************
* Copyright (C) 2009/2025 - Cristiano Lehrer (cristiano@ybadoo.com.br) *
* Ybadoo - Solucoes em Software Livre (ybadoo.com.br) *
* *
* Permission is granted to copy, distribute and/or modify this document *
* under the terms of the GNU Free Documentation License, Version 1.3 or *
* any later version published by the Free Software Foundation; with no *
* Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A *
* A copy of the license is included in the section entitled "GNU Free *
* Documentation License". *
* *
* Ubuntu 16.10 (GNU/Linux 4.8.0-39-generic) *
* OpenJDK Version "1.8.0_121" *
* OpenJDK 64-Bit Server VM (build 25.121-b13, mixed mode) *
*************************************************************************/
package com.ybadoo.tutoriais.poo.tutorial09.exercicio26;
/**
* Elementos utilizados para o calculo da media
*
* Abstraction define a interface da abstracao, mantendo uma referencia
* para um objeto do tipo Implementor (Gamma, 2000)
*/
public abstract class Element
{
/**
* Representacao da media
*/
protected Mean mean;
/**
* Inicializar a media a ser empregada
*
* @param mean media a ser empregada
*/
protected Element(Mean mean)
{
this.mean = mean;
}
/**
* Retorna a media dos elementos
*
* @return media dos elementos
*/
public abstract double getMean();
}/*************************************************************************
* Copyright (C) 2009/2025 - Cristiano Lehrer (cristiano@ybadoo.com.br) *
* Ybadoo - Solucoes em Software Livre (ybadoo.com.br) *
* *
* Permission is granted to copy, distribute and/or modify this document *
* under the terms of the GNU Free Documentation License, Version 1.3 or *
* any later version published by the Free Software Foundation; with no *
* Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A *
* A copy of the license is included in the section entitled "GNU Free *
* Documentation License". *
* *
* Ubuntu 16.10 (GNU/Linux 4.8.0-39-generic) *
* OpenJDK Version "1.8.0_121" *
* OpenJDK 64-Bit Server VM (build 25.121-b13, mixed mode) *
*************************************************************************/
package com.ybadoo.tutoriais.poo.tutorial09.exercicio26;
import java.util.List;
/**
* Elementos armazenados numa lista
*
* RefinedAbstraction estende a interface definida por
* Abstraction (Gamma, 2000)
*/
public class ElementList<T> extends Element
{
/**
* Elementos
*/
private List<T> values;
/**
* Inicializar os elementos e a media a ser empregada
*
* @param values elementos
* @param mean media a ser empregada
*/
public ElementList(List<T> values, Mean mean)
{
super(mean);
this.values = values;
}
/* (non-Javadoc)
* @see com.ybadoo.tutoriais.poo.tutorial09.exercicio26.Number#getMean()
*/
@Override
public double getMean()
{
return mean.average(values.toArray());
}
}/*************************************************************************
* Copyright (C) 2009/2025 - Cristiano Lehrer (cristiano@ybadoo.com.br) *
* Ybadoo - Solucoes em Software Livre (ybadoo.com.br) *
* *
* Permission is granted to copy, distribute and/or modify this document *
* under the terms of the GNU Free Documentation License, Version 1.3 or *
* any later version published by the Free Software Foundation; with no *
* Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A *
* A copy of the license is included in the section entitled "GNU Free *
* Documentation License". *
* *
* Ubuntu 16.10 (GNU/Linux 4.8.0-39-generic) *
* OpenJDK Version "1.8.0_121" *
* OpenJDK 64-Bit Server VM (build 25.121-b13, mixed mode) *
*************************************************************************/
package com.ybadoo.tutoriais.poo.tutorial09.exercicio26;
/**
* Elementos armazenados num vetor
*
* RefinedAbstraction estende a interface definida por
* Abstraction (Gamma, 2000)
*/
public class ElementVector extends Element
{
/**
* Elementos
*/
private Object[] values;
/**
* Inicializar os elementos e a media a ser empregada
*
* @param values elementos
* @param mean media a ser empregada
*/
public ElementVector(Object[] values, Mean mean)
{
super(mean);
this.values = values;
}
/* (non-Javadoc)
* @see com.ybadoo.tutoriais.poo.tutorial09.exercicio26.Number#getMean()
*/
@Override
public double getMean()
{
return mean.average(values);
}
}/*************************************************************************
* Copyright (C) 2009/2025 - Cristiano Lehrer (cristiano@ybadoo.com.br) *
* Ybadoo - Solucoes em Software Livre (ybadoo.com.br) *
* *
* Permission is granted to copy, distribute and/or modify this document *
* under the terms of the GNU Free Documentation License, Version 1.3 or *
* any later version published by the Free Software Foundation; with no *
* Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A *
* A copy of the license is included in the section entitled "GNU Free *
* Documentation License". *
* *
* Ubuntu 16.10 (GNU/Linux 4.8.0-39-generic) *
* OpenJDK Version "1.8.0_121" *
* OpenJDK 64-Bit Server VM (build 25.121-b13, mixed mode) *
*************************************************************************/
package com.ybadoo.tutoriais.poo.tutorial09.exercicio26;
import java.util.ArrayList;
import java.util.List;
/**
* Classe responsavel pela execucao do padrao Bridge
*/
public class Application
{
/**
* Construtor para inicializar a execucao do padrao Bridge
*/
private Application()
{
}
/**
* Metodo principal da linguagem de programacao Java
*
* @param args argumentos da linha de comando (nao utilizado)
*/
public static void main(String[] args)
{
Integer[] values = {1, 2, 3, 4, 5};
Element vector = new ElementVector(values, new ArithmeticMean());
System.out.println(vector.getMean());
List<Integer> listValues = new ArrayList<Integer>();
listValues.add(1);
listValues.add(2);
listValues.add(3);
listValues.add(4);
listValues.add(5);
Element list = new ElementList<Integer>(listValues, new ArithmeticMean());
System.out.println(list.getMean());
}
}Gamma, Erich. (2000). Padrões de Projeto: soluções reutilizáveis de software orientado a objetos. Porto Alegre: Bookman. 364 páginas.
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