import java.io.*;
import java.util.StringTokenizer;
public class Proj21110
{
private static int MAX_UNKNOWNS = 10;
public static void main (String[] args)
{
headerMessage(); // print header
BufferedReader in = null;
if(args.length > 0)
{
in = getReader(args[0]); // open file
System.out.println("Opened file: " + args[0]);
}
else
{
in = getReader("guess.data"); // open file
System.out.println("Opened file: " + "guess.data");
}
System.out.println();
printContents(in);
}
//////////////////////////////////////////////////////////////////////
/*
Prints out the Heading of the Program
*/
/////////////////////////////////////////////////////////////////////
private static void headerMessage()
{
System.out.println("CMSC256 Project 2 - Fall '08 - C. Walker");
System.out.println();
} //headerMessage
//////////////////////////////////////////////////////////////////////
/*
Open file
*/
/////////////////////////////////////////////////////////////////////
private static BufferedReader getReader(String name)
{
BufferedReader in = null;
try
{
File file = new File(name);
in = new BufferedReader(new FileReader(file));
}
catch (FileNotFoundException e)
{
System.out.println("The file doesn't exist.");
System.exit(0);
}
return in;
}
//////////////////////////////////////////////////////////////////////
/*
print contents
*/
/////////////////////////////////////////////////////////////////////
private static void printContents(BufferedReader in)
{
double[][] a = new double[MAX_UNKNOWNS][MAX_UNKNOWNS+1];
int i,j;
int numUnknowns = 0;
try{
String line = in.readLine();
while(line != null && line.length() > 0)
{
// read number of unknowns
numUnknowns = Integer.parseInt(line);
// print out unkowns
System.out.println("\nNumber of unknowns: " + numUnknowns);
// read in equations
for(i=0;i<numUnknowns;i++)
{
line = in.readLine();;
StringTokenizer tok = new StringTokenizer(line);
for(j=0;j<numUnknowns;j++)
{
a[i][j] = Double.parseDouble((tok.nextToken()));
if(j > 0)System.out.print(" + ");
System.out.print(a[i][j] + "x_" + (j+1));
}
a[i][j] = Double.parseDouble((tok.nextToken()));
System.out.println(" = " + a[i][j]);
}
gaussian(a, numUnknowns);
line = in.readLine();
} // end while
} // end try
catch (IOException e)
{
System.out.println("I/O Error");
System.exit(0);
}
catch(NumberFormatException ex)
{
System.out.println("Impropper number encountered in file");
System.exit(0);
}
}
//////////////////////////////////////////////////////////////////////
/*
gaussian elimination
*/
/////////////////////////////////////////////////////////////////////
private static void gaussian(double[][] a, int n)
{
int i,j,k;
double t;
double[] x = new double[n];
double sum;
// Step 1 For i = 1,...., n-1 do Steps 2 - 4. (Elimination Process)
for(i=0;i<n;i++){
// Step 2 Let p be the smallest integer with i <= p <= n and ap,i != 0.
int p = i;
boolean found = a[i][i]!=0;
for(j=i+1;j<n;j++)
{
if(a[i][j] != 0)found = true;
if(a[i][j] != 0 && Math.abs(a[j][i]) > Math.abs(a[i][p]))
{
p = j;
}
}
// If no integer p can be found then
//OUTPUT('singular matrix - no unique solution'); STOP.
if(!found)
{
System.out.println("singular matrix - no unique solution");
return;
}
// Step 3 If p != i then perform (Ep) <-> (Ei)
if(p!=i)
{
// swapping rows p and i
for(k=0;k<n+1;k++)
{
t = a[p][k];
a[p][k] = a[i][k];
a[i][k] = t;
}
}
if(a[i][i] == 0)
{
System.out.println("singular matrix - no unique solution");
return;
}
// Step 4 For j = i + 1,..., n do Steps 5 and 6.
for(j=i+1;j<n;j++) {
//Step 5 Set m=aji/aii.
double m = a[j][i] / a[i][i];
// Step 6 Perform (Ej - mEi) -> (Ej).
for(k=0;k<n+1;k++)
a[j][k] = a[j][k] - m * a[i][k];
}
}
// Step 7 If ann = 0 then OUTPUT('no unique solution exists'); STOP.
if(a[n-1][n-1] == 0)
{
System.out.println("singular matrix - no unique solution");
return;
}
// Step 8 Set xn = an,n+1=ann. (Start backward substitution)
x[n-1] = a[n-1][n] / a[n-1][n-1];
// Step 9 For i = n - 1,....,1 set xi = [ai, n+1 - sum aij,xj] / aii
for(i=n-2;i>= 0;i--)
{
sum = 0;
for(j=i+1;j<n;j++)
{
sum = sum + a[i][j] * x[j];
}
x[i] = (a[i][n] - sum) / a[i][i];
}
// Step 10 OUTPUT(x1,...., xn); (Procedure completed successfully)
// STOP.
printSolution(x, n);
}
//////////////////////////////////////////////////////////////////////
/*
print solution
*/
/////////////////////////////////////////////////////////////////////
private static void printSolution(double[]x, int n)
{
System.out.println("Solution: ");
for(int i=0;i<n;i++)
{
System.out.println("x_" + (i+1) + " = " + x[i]);
}
}
}
The file that im reading from is called gauss.data. It contains the following elements:
4
2 1 1 -6 -1
-3 6 -1 8 -20
1 1.0 1 -3 0
4 -2 8 -3 43
3
5 -1 -1 11
-1 5 -2 0
-2 -2 4 0
3
0 1 1 1
0 -2 -2 -8
0 0 -6 2
the error i get when i run the program is:
Exception in thread "main" java.util.NoSuchElementException
at java.util.StringTokenizer.nextToken(StringTokenizer.java:332)
at Proj21110.printContents(Proj21110.java:112)
at Proj21110.main(Proj21110.java:33)
It reads in the first elements, it recognizes that 4 is the number of unknowns, and it reads in 2, 2, -6, and -1 but then throws this error. What am I doing wrong?
