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citydude23 · Feb 5, 2016, 03:33 PM

I need help multiplying 2d arrays from and input file (input.txt) and I need help writing their multiplied outputs to and output file(output.txt) Why isn't my method showNewArray working?

input.txt:
9 3
8 5
2 3 3 8
2 1 1 2
3 3 5 9
2 2 3
3 4 6
8 9 7 6
(edit: sorry wrote the question really fast!)
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
public class hw1 {
public int[][] showNewArray(int[][] matrix1, int[][] matrix2){// mulitplies two matrixes together
int[][] matrix3 = new int[matrix1.length][matrix2.length];// takes the lengths from matrix1&&matrix2
for(int i =0;i <matrix1.length;i++){
for(int j =0; j<matrix2[0].length;j++){//column length of matrix2
for(int k =0; k< matrix1[0].length;k++){//column length of matrix1
matrix3[i][j] += matrix1[i][k] * matrix2[k][j];// multiplies em
}
}
}
showNewArray(matrix3[][]);
}
public static void main(String args[]){
FileReader fileReader = null;
FileWriter fileWriter = null;
BufferedReader bufferedReader = null;
try {
fileReader = new FileReader("C:/javastuff/principles/input.txt");
fileWriter = new FileWriter("C:/javastuff/principles/output.txt",true);
bufferedReader = new BufferedReader(fileReader);
int flag=0;
String line = null;//initialization
String words[];
int lineCount = 0;
int row1=0, column1=0, row2=0, column2=0;
String fileData[] = new String[100];//we are assuming the file won't contain more than 100 lines, but this is clearly a drawback
while ((line = bufferedReader.readLine()) != null){
System.out.println(line);//to check that code is reading file line by line
if(!line.trim().equals("")){//we ignore the blank lines
words = line.trim().split("\\s+"); //split the line in words separated by spaces
if(lineCount==0){
row1 = Integer.parseInt(words[0]);
column1 = Integer.parseInt(words[1]);
}
else if(lineCount==1){
row2 = Integer.parseInt(words[0]);
column2 = Integer.parseInt(words[1]);
if(column1!=row2){
flag = 1;
break;
}
}
else{
fileData[lineCount] = line;
}
lineCount++;
}
}
if(flag==1){
System.out.println("Invalid input.");
fileWriter.write("Invalid input.");
}else{
int[][] matrix1=new int[row1][column1];
int[][] matrix2=new int[row2][column2];
int fileRow=0;
for(int index=2;index<row1+2;index++) {
line = fileData[index];
if(!line.trim().equals("")){//we ignore the blank lines
words=line.trim().split("\\s+");
for (int col = 0; col < words.length; col++) {
matrix1[fileRow][col] = Integer.parseInt(words[col]);
}
fileRow++;
}
}
System.out.println("matrix1:");
fileWriter.write("\nmatrix1:\n");
for(int p =0;p<row1;p++){
for(int q =0;q<column1;q++){
System.out.print(matrix1[p][q]+" ");
fileWriter.write(matrix1[p][q]+" ");
}
System.out.println();
fileWriter.write("\n");
}
fileRow=0;
for(int index=row1+2;index<row2+row1+2;index++) {
line = fileData[index];
if(!line.trim().equals("")){//we ignore the blank lines
words=line.trim().split("\\s+");
for (int col2 = 0; col2 < words.length; col2++) {
matrix2[fileRow][col2] = Integer.parseInt(words[col2]);
}
fileRow++;
}
}
System.out.println("matrix2:");
fileWriter.write("\nmatrix2:\n");
for(int p =0;p<row2;p++){
for(int q =0;q<column2;q++){
System.out.print(matrix2[p][q]+" ");
fileWriter.write(matrix2[p][q]+" ");
}
System.out.println();
fileWriter.write("\n");
}
}
bufferedReader.close();
fileReader.close();
fileWriter.close();
}
catch (NumberFormatException e) {
e.printStackTrace();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
showNewArray MpliedTogether = new showNewArray(matrix1[][], matrix2[][]);
}
}

Kristofer · Mar 11, 2016, 05:16 PM

This makes no sense. Is this written by a computer?

Alty · Mar 11, 2016, 05:35 PM

Is this homework?