title: System.setProperty and System.getProperty
body: <p>I didn't understand when I used <code>System.setProperty</code> to define a parameter, where the data is stored? </p>
  
  <p>If say that I used <code>System.setProperty</code> in one java file, then can I use the properties anywhere? But this is not true, I can't use it anywhere, only in the same java file I called <code>setProperty</code>.</p>
  
  <p>I really do not know why and what the function of this method is.</p>