This is a problem I've been having, When making a set number of filled circles at random locations on a JPanel and applying a gravity (a negative change in the y), each of the circles collide. I want them to have collision detection and push in the opposite direction using vectors but I don't know how to apply that to my scenario could someone help?

public void drawballs(Graphics g){
    g.setColor (Color.white); 

    //displays circles
    for(int i = 0; i<xlocationofcircles.length-1; i++){
    g.fillOval( (int) xlocationofcircles[i],  (int) (ylocationofcircles[i]) ,16 ,16 );
    ylocationofcircles[i]+=.2; //gravity
    if(ylocationofcircles[i] > 550) //stops gravity at bottom of screen
    ylocationofcircles[i]-=.2;

    //Check distance between circles(i think..)
    float distance =(xlocationofcircles[i+1]-xlocationofcircles[i]) + (ylocationofcircles[i+1]-xlocationofcircles[i]);

    if( Math.sqrt(distance) <16)
    ...