title: Pre-condition vs Post-condition in java?
body: <p>For example I have the following code:</p>
  
  <pre><code>public class Calc(){
    final int PI = 3.14; //is this an invariant?
  
    private int calc(int a, int b){ 
        return a + b;
        //would the parameters be pre-conditions and the return value be a post-condition?
    }
  }
  </code></pre>
  
  <p>I am just confused on what exactly these terms mean? The code above is what I think it is, however can anyone point me into the right direction with my theory?</p>