Android : get Integer value from EditText Android

This is my activity.xml

<EditText
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:id="@+id/inputnumber"
 android:inputType="number" />

this is mainactivity.java :

EditText num = (EditText) findViewById(R.Id.inputnumber) ;

the question is how can I get the integer value from this field as an integer and use it for example in a custom class I made like this to add 1 to the value of this input field?

my customclass.java

public static int addone(int a) 
{
  int b = a+1;
  return b;
}