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# Guassian Elimination

If you export a runnable jar file you can execute this from a Terminal window with the command (actually "Terminal" is for Mac OSX or linux, for Windows Use "Command Prompt" from the Start > All Programs >Accessories menu)

java -jar GEApp.jar


# Rational.java



public class Rational {
private int numerator;
private int denominator;
public Rational(String s){
int fBar=s.indexOf("/");
if (fBar==-1){
numerator=Integer.parseInt(s);
denominator=1;
} else {
numerator=Integer.parseInt(s.substring(0,fBar));
denominator=Integer.parseInt(s.substring(fBar+1));
simplify();
}
}
public Rational(int n, int d){
numerator=n;
denominator=d;
simplify();
}
public Rational(int n){
numerator=n;
denominator=1;
}
public Rational(){
numerator=0;
denominator=1;
}
public Rational (Rational r){
this.numerator=r.getNumerator();
this.denominator=r.getDenominator();
}
public void setNumerator(int numerator) {
this.numerator = numerator;
}
public int getNumerator() {
return numerator;
}
public void setDenominator(int denominator) {
this.denominator = denominator;
}
public int getDenominator() {
return denominator;
}
public double value(){
return (double)(numerator)/denominator;
}
public String toString(){
if (denominator ==1)
return Integer.toString(numerator);
return Integer.toString(numerator)+"/"+Integer.toString(denominator);
}
public Rational multiply(Rational other){
int n=this.getNumerator()*other.getNumerator();
int d=this.getDenominator()*other.getDenominator();
Rational result=new Rational(n,d);
return result;
}
int n=this.getNumerator()*other.getDenominator()+
other.getNumerator()*this.getDenominator();
int d=this.getDenominator()*other.getDenominator();
Rational result=new Rational(n,d);
return result;
}

public void simplify(){
int p=2;
while (p<= Math.max(numerator, denominator)){
while(numerator%p==0 && denominator%p==0){
numerator/=p;
denominator/=p;
}
if (p==2) p++; else p+=2;
}
}
}


# Equation.java



public class Equation {
private Rational x;
private Rational y;
private Rational z;
private Rational c;
public Equation(String xCoeff, String yCoeff, String zCoeff, String constant){
x=new Rational(xCoeff);
y=new Rational(yCoeff);
z=new Rational(zCoeff);
c=new Rational(constant);
}
public Equation (Rational x, Rational y, Rational z, Rational c){
this.x=x;
this.y=y;
this.z=z;
this.c=c;
}
public Equation (Equation e){
this.x=e.getX();
this.y=e.getY();
this.z=e.getZ();
this.c=e.getC();
}
public Equation (){
this.x=new Rational();
this.y=new Rational();
this.z=new Rational();
this.c=new Rational();
}
public Rational getX(){
return x;
}
public Rational getY(){
return y;
}
public Rational getZ(){
return z;
}
public Rational getC(){
return c;
}
public void setX(String r){
this.x=new Rational(r);
}
public void setX(Rational r){
this.x=r;
}
public void setY(String r){
this.y=new Rational(r);
}
public void setY(Rational r){
this.y=r;
}
public void setZ(String r){
this.z=new Rational(r);
}
public void setZ(Rational r){
this.z=r;
}
public void setC(String r){
this.c=new Rational(r);
}
public void setC(Rational r){
this.c=r;
}
public String toString(){
return "("+x.toString()+")x + ("+y.toString()+")y + ("+z.toString()+")z = "+c.toString();
}
public Equation multiply(Rational r){
return new Equation (x.multiply(r), y.multiply(r), z.multiply(r), c.multiply(r));
}
public Equation multiply(Rational r, Equation other){
Equation e= other.multiply(r);
}
}


# GEApp.java (this is if you want to run this as an application)


import java.util.Scanner;

public class GEApp {
static Scanner in;
static Equation[] row;
public static void main(String[] args) {
in=new Scanner(System.in);
row=new Equation[3];
for (int i=0;i<3;i++)
row[i]=new Equation();
String command=getCommand();
while(!command.equals("Q")){
if (command.equals("E")){
int r=getRow("Edit which row (1-3): ");
row[r].setX(getRational("Coeff of x: "));
row[r].setY(getRational("Coeff of y: "));
row[r].setZ(getRational("Coeff of z: "));
row[r].setC(getRational("equals: "));

} else if (command.equals("S")){
int a=getRow("Swap row (1-3): ");
int b=getRow("with what row (1-3): ");
Equation buffer=new Equation(row[a]);
row[a]=row[b];
row[b]=buffer;
} else if (command.equals("M")){
Rational number=getRational("Number to multiply: ");
int r=getRow("Multiply "+number.toString()+" to which row (1-3): ");
row[r]=row[r].multiply(number);
} else if (command.equals("A")){
Rational number=getRational("Number to multiply: ");
int a=getRow("Multiply "+number.toString()+" to which row (1-3): ");
int r=getRow("And add it to which row (1-3): ");
row[r]=row[r].multiply(number, row[a]);
}

command=getCommand();
}
}
public static String getCommand(){
System.out.println("System of Equations:");
for (Equation e:row)
System.out.println(e);
System.out.print("Menu: E)dit, S)wap, M)ultiply a row, A)dd a multiple of a row, Q)uit > ");
String command=in.nextLine();
command=command.toUpperCase();
return command.substring(0, 1);
}
public static int getRow(String prompt){
System.out.print(prompt);
String row = in.nextLine();
int result = Integer.parseInt(row);
while (result < 1 || result > 3){
System.out.print(prompt);
row = in.nextLine();
result = Integer.parseInt(row);
}
return result-1;
}
public static Rational getRational(String prompt){
System.out.print(prompt);
return new Rational(in.nextLine());
}

}


# GECounsoleApplet.java (This is if you want to make an Applet version to run in a web browser using The ConsoleApplet


@SuppressWarnings("serial")
public class GEConsoleApplet extends ConsoleApplet
{

private Equation[] row;
protected String getTitle() {
return  "Guassian Elimination Applet";
}
public  String getCommand(){
console.putln("System of Equations:");
for (Equation e:row)
console.putln(e.toString());
console.put("Menu: E)dit, S)wap, M)ultiply a row, A)dd a multiple of a row, Q)uit > ");
String command=console.getln();
command=command.toUpperCase();
return command.substring(0, 1);
}
public  int getRow(String prompt){
console.putln(prompt);
String row = console.getln();
int result = Integer.parseInt(row);
while (result < 1 || result > 3){
console.put(prompt);
row = console.getln();
result = Integer.parseInt(row);
}
return result-1;
}
public  Rational getRational(String prompt){
console.put(prompt);
return new Rational(console.getln());
}
public void program(){
row=new Equation[3];
for (int i=0;i<3;i++)
row[i]=new Equation();
String command=getCommand();
while(!command.equals("Q")){
if (command.equals("E")){
int r=getRow("Edit which row (1-3): ");
row[r].setX(getRational("Coeff of x: "));
row[r].setY(getRational("Coeff of y: "));
row[r].setZ(getRational("Coeff of z: "));
row[r].setC(getRational("equals: "));

} else if (command.equals("S")){
int a=getRow("Swap row (1-3): ");
int b=getRow("with what row (1-3): ");
Equation buffer=new Equation(row[a]);
row[a]=row[b];
row[b]=buffer;
} else if (command.equals("M")){
Rational number=getRational("Number to multiply: ");
int r=getRow("Multiply "+number.toString()+" to which row (1-3): ");
row[r]=row[r].multiply(number);
} else if (command.equals("A")){
Rational number=getRational("Number to multiply: ");
int a=getRow("Multiply "+number.toString()+" to which row (1-3): ");
int r=getRow("And add it to which row (1-3): ");
row[r]=row[r].multiply(number, row[a]);
}

command=getCommand();
}
}
}