title: How to generate a hash code from three longs
body: <p>I have a HashMap with coordinates as keys.</p>
  
  <p>Coordinates have 3 longs holding the x, y and z coordinate. (Coordinate is and needs to be a custom class, the coordinates need to be longs).</p>
  
  <p>Now i want to be able to access e.g. the field [5, 10, 4] by doing: <code>hashMap.get(new Coordinate(5, 10, 4))</code>.</p>
  
  <p>I have implemented the equals method but that is not enough since apparently i need to provide an implementation for hashCode as well. So my question is <b>how do i generate an unique hashCode from three longs?</b>.</p>
  
  <p>Additional: Using a hash generator from an external library is not option.</p>