Tutoriais - Programação Orientada a Objetos
Tutoriais
Programação Orientada a Objetos

/**
 * Copyright (C) 2009/2024 - Cristiano Lehrer (cristiano@ybadoo.com.br)
 *                  Ybadoo - Solucoes em Software Livre (www.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 copy of the license is included in the section entitled "GNU
 * Free Documentation License".
 */

package com.ybadoo.tutoriais.poo;

/**
 * Component
 */
public interface Expressao
{
  /**
   * Resolver a expressao aritmetica
   * 
   * @return resultado da expressao aritmetica
   */
  public int resolver();
}

/**
 * Copyright (C) 2009/2024 - Cristiano Lehrer (cristiano@ybadoo.com.br)
 *                  Ybadoo - Solucoes em Software Livre (www.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 copy of the license is included in the section entitled "GNU
 * Free Documentation License".
 */

package com.ybadoo.tutoriais.poo;

/**
 * Leaf
 */
public class Constante implements Expressao
{
  /**
   * Valor da constante numerica
   */
  private int valor;
  
  /**
   * Construtor para inicializar o valor da constante numerica
   * 
   * @param valor valor da constante numerica
   */
  public Constante(int valor)
  {
    this.valor = valor;
  }
  
  /* (non-Javadoc)
   * @see com.ybadoo.tutoriais.poo.Expressao#resolver()
   */
  public int resolver()
  {
    return this.valor;
  }

  /* (non-Javadoc)
   * @see java.lang.Object#toString()
   */
  public String toString()
  {
    return new Integer(this.valor).toString();
  }
}

/**
 * Copyright (C) 2009/2024 - Cristiano Lehrer (cristiano@ybadoo.com.br)
 *                  Ybadoo - Solucoes em Software Livre (www.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 copy of the license is included in the section entitled "GNU
 * Free Documentation License".
 */

package com.ybadoo.tutoriais.poo;

/**
 * Composite
 */
public class Operacao implements Expressao
{
  /**
   * Operador da operacao
   */
  private char operador;
  
  /**
   * Primeiro operando da operacao
   */
  private Expressao operandoA;
  
  /**
   * Segundo operando da operacao
   */
  private Expressao operandoB;
  
  /**
   * Construtor para inicializar a operacao
   * 
   * @param operandoA primeiro operando da operacao
   * @param operador operador da operacao
   * @param operandoB segundo operando da operacao
   */
  public Operacao(Expressao operandoA, char operador, Expressao operandoB)
  {
    this.operandoA = operandoA;
    
    this.operador = operador;
    
    this.operandoB = operandoB;
  }
  
  /* (non-Javadoc)
   * @see com.ybadoo.tutoriais.poo.Expressao#resolver()
   */
  public int resolver()
  {
    if(this.operador == '+')
    {
      return this.operandoA.resolver() + this.operandoB.resolver();
    }
    else if(this.operador == '-')
    {
      return this.operandoA.resolver() - this.operandoB.resolver();
    }
    else if(this.operador == '*')
    {
      return this.operandoA.resolver() * this.operandoB.resolver();
    }
    else if(this.operador == '/')
    {
      return this.operandoA.resolver() / this.operandoB.resolver();
    }
    
    return 0;
  }
  
  /* (non-Javadoc)
   * @see java.lang.Object#toString()
   */
  public String toString()
  {
    return "(" + this.operandoA + " " + this.operador + " " + this.operandoB + ")";
  }
}

/**
 * Copyright (C) 2009/2024 - Cristiano Lehrer (cristiano@ybadoo.com.br)
 *                  Ybadoo - Solucoes em Software Livre (www.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 copy of the license is included in the section entitled "GNU
 * Free Documentation License".
 */

package com.ybadoo.tutoriais.poo;

/**
 * Client
 */
public class Calculadora
{
  /**
   * Metodo principal da linguagem de programacao Java
   * 
   * @param args argumentos da linha de comando (nao utilizado)
   */
  public static void main(String[] args)
  {
    Operacao op1 = new Operacao(new Constante(5), '+', new Constante(7));
    
    System.out.println(op1 + " = " + op1.resolver()); // (5 + 7) = 12
    
    Operacao op2 = new Operacao(new Constante(3), '*', op1);
    
    System.out.println(op2 + " = " + op2.resolver()); // (3 * (5 + 7)) = 36
    
    Operacao op3 = new Operacao(op2, '/', new Constante(4));
    
    System.out.println(op3 + " = " + op3.resolver()); // ((3 * (5 + 7)) / 4) = 9
  }
}