why can not the value of primitive type variable be changed?
<pre><code>    public class testtype
{
  private   int a;
  private double b;

   testtype(int a,double b)
  {
    this.a=a;
    this.b=b;
  }

  public void maketoequal(testtype oo)
  {
    oo.a=this.a;
    oo.b=this.b;
  }

  void trytoequal(int c)
  {
    c=this.a;
  }

  public static void main(String[] args)
  {
    testtype t1,t2;
    t1=new testtype(10,15.0);
    t2=new testtype(5,100.0);
    t1.maketoequal(t2);
    System.out.println("after the method is called:"+"\n"+"the value of a for t2 is:"+t2.a
    +"\n"+"the value of b for t2 is :"+t2.b);
    int c=50;
    t1.trytoequal(c);
    System.out.println("the value of c after the method be called is:"+c);
  }
}
</code></pre>

<p>why the c is not changed? </p>
