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Problema

Defina uma nova classe que represente uma porta lógica AND com três entradas. Esta classe deve chamar-se AndGate3 e apresenta a mesma funcionalidade que a de duas entradas. A apresentação (toString) é A: valor B: valor C: valor.

A classe AndGate3 deve ser definida reutilizando o conceito AndGate2 (definido no Exercício 1).

Adapte a função main definida anteriormente, por forma a integrar alguns testes com a nova porta lógica.

Solution 1: AndGate3i defined as a subclass of AndGate2

In this solution we observe that the operation is a specialization of the previous one. This allows us to reuse the previous functionality.

<java5> /** Logical AND gate (inheritance). */ public class AndGate3i extends AndGate2 { /** A new input is needed (the other two are inherited). */ private boolean _c = false;

/** * Default constructor: false for all inputs. */ public AndGate3i() { //super(); //default: explicit call not needed }

/** * Inputs receive same value. * * @param v * the input value. */ public AndGate3i(boolean v) { super(v); _c = v; }

/** * Arbitrary input value combinations. * * @param a * input value * @param b * input value * @param c * input value */ public AndGate3i(boolean a, boolean b, boolean c) { super(a, b); _c = c; }

/** * @return third input value. */ public boolean getC() { return _c; }

/** * Set input value. * * @param c * input value. */ public void setC(boolean c) { _c = c; }

/** * @return value of logical AND operation. */ @Override public boolean getOutput() { return super.getOutput() && _c; }

/** * @see java.lang.Object#equals(java.lang.Object) */ @Override public boolean equals(Object other) { if (other instanceof AndGate3i) { AndGate3i andGate = (AndGate3i) other; return super.equals(other) && _c == andGate.getC(); } return false; }

/** * @see java.lang.Object#toString() */ @Override @SuppressWarnings("nls") public String toString() { return super.toString() + " C:" + _c; } } </java5>

Solução 2: AndGate3c defined as a composition of two AndGate2

In this solution, the 3-input gate is defined as a composition of 2-input gates. Note that the A-input of the second gate is updated whenever the inputs of the first gate are changed.

<java5> /** Logical AND gate with 3 inputs (composition). */ public class AndGate3c { /** The first gate takes inputs 'a' and 'b' */ private AndGate2 _gate1;

/** * The second gate takes as inputs the output of the first gate (input 'a') * and 'c' (input 'b') */ private AndGate2 _gate2;

/** * Default constructor: false for all inputs. */ public AndGate3c() { _gate1 = new AndGate2(); _gate2 = new AndGate2(_gate1.getOutput(), false); }

/** * Inputs receive same value. * * @param v * the input value. */ public AndGate3c(boolean v) { _gate1 = new AndGate2(v); _gate2 = new AndGate2(_gate1.getOutput(), v); }

/** * Arbitrary input value combinations. * * @param a * input value * @param b * input value * @param c * input value */ public AndGate3c(boolean a, boolean b, boolean c) { _gate1 = new AndGate2(a, b); _gate2 = new AndGate2(_gate1.getOutput(), c); }

/** * @return first input value. */ public boolean getA() { return _gate1.getA(); }

/** * Set input value. * * @param a * input value. */ public void setA(boolean a) { _gate1.setA(a); _gate2.setA(_gate1.getOutput()); }

/** * @return second input value. */ public boolean getB() { return _gate1.getB(); }

/** * Set input value. * * @param b * input value. */ public void setB(boolean b) { _gate1.setB(b);

               _gate2.setA(_gate1.getOutput());

}

/** * @return second input value. */ public boolean getC() { return _gate2.getB(); }

/** * Set input value. * * @param c * input value. */ public void setC(boolean c) { _gate2.setB(c); }

/** * Since the two gates are always kept in sync, we only need to ask for the * output of the second gate. * * @return value of logical AND operation. */ public boolean getOutput() { return _gate2.getOutput(); }

/** * @see java.lang.Object#equals(java.lang.Object) */ @Override public boolean equals(Object other) { if (other instanceof AndGate3c) { AndGate3c ag = (AndGate3c) other; return getA() == ag.getA() && getB() == ag.getB() && getC() == ag.getC(); } return false; }

/** * @see java.lang.Object#toString() */ @Override @SuppressWarnings("nls") public String toString() { return "A:" + getA() + " B:" + getB() + " C:" + getC(); } } </java5>