Make an if statement less cluttered [duplicate]

This question already has an answer here:

• Best way to format multiple 'or' conditions in an if statement (Java) 7 answers

Is there some way to improve this if statement i have

if((monthBox.getSelectedIndex()==0)||(monthBox.getSelectedIndex()==2)||(monthBox.getSelectedIndex()==4)||(monthBox.getSelectedIndex()==6)||(monthBox.getSelectedIndex()==7)||(monthBox.getSelectedIndex()==9)||(monthBox.getSelectedIndex()==11)){
    for(int i=0;i<=31;i++){
        dayBox.addItem(i);
    }
}

I have a bunch of months which the user selects one from and then with that month it populates another combobox with the amount of days that month has.

Is there some way to do something like this

 if(monthBox.getSelectedIndex()==1,2,...){
 //code here
 }