Below is the syntax highlighted version of FourChargeClient.java.
/* Book Exercise 3.1.1 to create a Charge client */ public class FourChargeClient { public static void main(String[] args) { // read in distance r from command line double r = Double.parseDouble(args[0]); // center of standard drawing window double cx = 0.5; double cy = 0.5; // construct four charges Charge c1 = new Charge(cx + r, cy, 1.0); // east Charge c2 = // south Charge c3 = // west Charge c4 = // north // Compute potentials at (.25, .5) double px = 0.25; double py = 0.5; double v1 = c1.potentialAt( ); double v2 = double v3 = double v4 = // compute and output total potential double sum = System.out.println("total potential = " + sum); } }