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.equals() mit hashCode() und JavaDoc in Java
/**
* Das ist eine Klasse für Komplexe Zahlen,
* welche die {@link Double} Klasse verwendet.
*
* <ul>
* <li>{@link Complex#add(complexnumbers.Complex) addiert komplexe zahlen}</li>
* </ul>
*
* @author Harald Schilly
*/
public class Complex {
/** realteil */
private double real;
/** imaginärteil */
private double imag;
public Complex(double real, double imag) {
this.real = real;
this.imag = imag;
}
public Complex(double real) {
this(real, 0.0);
}
public Complex() { this(0,0); }
/**
* Addiert zu dieser {@link Complex komplexe Zahl} eine andere
*.
* @param other die andere Zahl
* @return gibt eine <b>NEUE</b> komplexe Zahl zurück
*/
public Complex add(Complex other) {
double r = this.real + other.real;
double i = this.imag + other.imag;
return new Complex(r, i);
}
/**
* Skaliert diese komplexe Zahl
*/
public void scale(double s) {
this.real *= s;
this.imag *= s;
}
/**
* Der <a href="http://en.wikipedia.org/wiki/Hashcode">Hashcode</a>
* eines Objektes muss für zwei Objekte, deren {@link #equals(Object) Vergleichstest}
* <code>true</code> ergibt, derselbe sein!
*/
@Override
public int hashCode() {
int hr = Double.valueOf(real).hashCode();
int hi = Double.valueOf(imag).hashCode();
return hr * 31 + hi;
}
/**
* Gleichzeitstest für andere Komplexe Zahlen Objekte und Doubles
*/
@Override
public boolean equals(Object other) {
if (this == other) {
return true;
}
if (other instanceof Complex){
Complex co = (Complex) other;
return real == co.real && imag == co.imag;
}
if (other instanceof Double) {
Double d = (Double) other;
return d.equals(real) && imag == 0;
}
return false;
}
@Override
public String toString() {
return real + "+" + imag + "i";
}
}
public class ComplexTest {
public static void main(String[] args) throws ParseException {
Complex c1 = new Complex(1.5, -.5);
Complex c2 = new Complex(1.5, -.5);
Complex c3 = c1.add(c2);
System.out.println("c1: " + c1);
System.out.println("c2: " + c2);
System.out.println("c1 + c2: " + c3);
Complex c4 = new Complex();
System.out.println("c4: " + c4);
System.out.println(" == :" + (c1 == c2));
System.out.println("equals: " + c1.equals(c2));
System.out.println("hashcode(c1): " + c1.hashCode());
System.out.println("hashcode(c2): " + c2.hashCode());
Double d = new Double(3);
Complex e = new Complex(3, 0);
System.out.println("equals: " + e.equals(d));
}
}
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