In.java

Object Oriented Design Revisited

/*************************************************************************
 *  Compilation:  javac Charge.java
 *  Execution:    java Charge x y
 *
 *************************************************************************/

public class Charge {
    private double rx, ry;   // position
    private double q;        // charge

    public Charge(double x0, double y0, double q0) {
        rx = x0;
        ry = y0;
        q  = q0;
    }

    public double potentialAt(double x, double y) {
        double k = 8.99e09;
        double dx = x - rx;
        double dy = y - ry;
        return k * q / Math.sqrt(dx*dx + dy*dy);
    }

    public String toString() {
        return q + " at " + "(" + rx + ", " + ry + ")";
    }

    public static void main(String[] args) {
        double x = Double.parseDouble(args[0]);
        double y = Double.parseDouble(args[1]);
        Charge c1 = new Charge(.51, .63, 21.3);
        Charge c2 = new Charge(.13, .94, 81.9);
        System.out.println(c1);
        System.out.println(c2);
        double v1 = c1.potentialAt(x, y);
        double v2 = c2.potentialAt(x, y);
        StdOut.println(v1+v2);
    }
}


Copyright © 2000–2010, Robert Sedgewick and Kevin Wayne. 
Last updated: Wed Feb 9 09:07:43 EST 2011.

Basic elements of a data type.

• API.
• Class.
• Access modifiers.
• Instance variables.
• Constructors.
• Instance methods.
• Variable names in methods.

Basic components that you need to understand to be able to build data types in Java.

NOTE:

You should be working on the programming assignment and gradient assignments before you start working on OOD programs.