I am having some issues with classes here. First of all, I have a Computer class that I have built that works fine with a separate "SystemBuilder" class. Everything in the class works fine. I am now building a separate class in order to store an array of objects. One of the requirements of this class is that I create an array of objects, have an add method, have a toString method, and a search method.
Well, I finished adding the toString method - and cannot get it to work quite right. While I understand the basic concept of everything that's going on here, the class relations are a bit confusing.
What seems to be happening now when I call the toString function on an object from my Object Collection Class (ComputerStore), it will call the toString method from the Computer class and print it in that format. However, I don't want that to happen to a ComputerStore object, I only want that to happen to Computer Objects.
Can someone please guide me in the way that I need to go here, and shed a little light into whats going on?
Thanks very much... Below is Computer Class first then ComputerStore class.
//This program will create Computer objects with different data members
//and will also upgrade those data members based on setters. This program
//also has a depreciation function and upgrade function. This (Computer) is the class
//and the SystemBuilder class is the class used for creating the objects.
public class Computer {
// Data Members - These belong to the class and are private.
// They all go to new objects.
private String cpu;
private int ram;
private String gpu;
private String motherboard;
private String psu;
private double cost;
private int serialnumber;
private double depreciation;
// Initial constructor with no arguments
Computer() {
cpu = "";
ram = 0;
gpu = "";
motherboard = "";
psu = "";
cost = 0.0;
serialnumber = 0;
depreciation = 0.0;
}
// Constructor with data members
Computer(String c, int r, String g, String m, String p, double co, int sn, double d) {
cpu = new String(c);
ram = r;
gpu = new String(g);
motherboard = new String(m);
psu = new String(p);
cost = co;
serialnumber = sn;
depreciation = d;
}
// Getters, allow retrieval of data members from outside of class
public String getCpu() {
return cpu;
}
public int getRam() {
return ram;
}
public String getGpu() {
return gpu;
}
public String getMotherboard() {
return motherboard;
}
public String getPsu() {
return psu;
}
public double getCost() {
return cost;
}
public int getSerialnumber() {
return serialnumber;
}
public double getDepreciation() {
return depreciation;
}
// Setters, allow setting of data members from outside of class
public void setCpu(String c) {
cpu = new String(c);
}
public void setRam(int r) {
ram = r;
}
public void setGpu(String g) {
gpu = new String(g);
}
public void setMotherboard(String m) {
motherboard = new String(m);
}
public void setPsu(String p) {
psu = new String(p);
}
public void setCost(double co) {
cost = co;
}
public void setSerialnumber(int sn) {
serialnumber = sn;
}
public void setDepreciation(double d) {
depreciation = d;
}
// Boolean below will compare computers to see if equal
// based on same motherboard SN#.
public boolean equals(Computer c) {
if (this.serialnumber == (c.serialnumber)) {
return true;
} else {
return false;
}
}
// To string method will print characteristics about object.
public String toString() {
return ("CPU:\t\t" + cpu + "\n" + "RAM:\t\t" + ram + "\n" + "GPU:\t\t" + gpu + "\n" + "Motherboard:\t"
+ motherboard + "\n" + "PSU:\t\t" + psu + "\n" + "Cost:\t\t" + "$" + cost + "\n" + "SN#:\t\t"
+ serialnumber + "\n" + "Depreciation:\t" + "$" + depreciation + " (annually)");
}
// A method to depreciate the cost of the computer
// The formula is observed below, but this is a
// straight line depreciation equation, calculated based
// on the values the user passes into the function. This method
// will show an output of annual depreciation based on useful
// life, entered in "years" by the user.
public void depreciate(double purchasePrice, double salvageValue, double lifeSpanYears) {
double depreciableCost;
double annualDepreciation;
depreciableCost = purchasePrice - salvageValue;
annualDepreciation = depreciableCost / lifeSpanYears;
depreciation = annualDepreciation;
}
// A method to upgrade the ram or the video card
// The method will accpet argumetns for ram (in int) and a gpu (string).
public void upgrade(int newRam, String newGpu) {
ram = newRam;
gpu = new String(newGpu);
}
}
public class ComputerStore {
private Computer[] systems;
private int sysNumbers;
public ComputerStore() {
systems = new Computer[200];
sysNumbers = 0;
}
public void add(String c, int r, String g, String m, String p, double co, int sn, double d)
{
systems[sysNumbers++] = new Computer(c, r, g, m, p, co, sn, d);
}
public String toString() {
String result = "";
for (int i = 0; i < sysNumbers; i++)
result += systems[i].toString() + "\n";
return result;
}
}
A ComputerStore.toString
is a text of which every line is a Computer.toString
. Misleading is the indentation and the {}.
public String toString() {
String result = "";
for (int i = 0; i < sysNumbers; i++)
result += systems[i].toString() + "\n";
return result;
}
More clear as code and as result would be:
public String toString() {
StringBuilder result = new StringBuilder("{");
for (int i = 0; i < sysNumbers; i++) {
if (i > 0) {
result.append(", ");
}
result.append(systems[i].getSerialNumber());
}
result.append("}");
return result.toString();
}
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