How to set onChecked Condition on CheckBoxes

I got two CheckBoxes Let us consider it as ChckBx1 and ChckBx2.

Now I need to implement few methods call on checkBoxes checked or not.

For more clearance, if chckBx1 checked then call Method1, if ChckBx2 is checked call Method2 and if Both CheckBoxes are checked Call Method3.

Please, provide few codes or examples.

Any help is appreciated.