Jak zamrozić przycisk w Javie?

import javax.swing.*;

public int[] zamrozone = new int[4];

a1 = new JButton("A1");
a2 = new JButton("A2");
a3 = new JButton("A2");
a4 = new JButton("A2");
a5 = new JButton("A2");

   private void zamroz()
    {

        zamrozone[0]=1;
        zamrozone[1]=1;
        zamrozone[2]=1;
        zamrozone[3]=0;
        zamrozone[4]=0;

        for(int i=0; i<8; i++) //losuje 8 statkow
            {
                if(zamrozone[i]==1)
                   "a"+i.setEnabled(false); // here is an error
            }
    }

zamrozone[is].setEnabled(false);

cannot find symbol symbol: 
method setEnabled(boolean)
location: class String