Question

Java Linked Lists

I want a simple program that reads two text files that contains an integers matrix and store each file into a linked lists matrix

so I can later preform operations such as addition and subtraction on the matrices

an example of the input text files:

sample a

2 6 2
6 2 18
17 11 20

sample b

3 13 5
4 11 20
13 18 20

Answer 1

import java.io.File;
import java.io.FileNotFoundException;
import java.util.LinkedList;
import java.util.Scanner;

public class MatrixReader {
        
        public static LinkedList<Integer> readMatrix(String fileName) {
                
                try {
                        Scanner in = new Scanner(new File(fileName));
                        LinkedList<Integer> matrix = new LinkedList<>();
                        
                        while(in.hasNextInt()) {
                                matrix.add(in.nextInt());
                        }
                        
                        in.close();
                        
                        return matrix;
                } catch (FileNotFoundException e) {
                        return null;
                }
        }
        
        public static LinkedList<Integer> addMatrices(LinkedList<Integer> l1,
                        LinkedList<Integer> l2) {

                LinkedList<Integer> result = new LinkedList<>();
                
                int size = l1.size();
                if(l2.size() < size) {
                        size = l2.size();
                }
                for(int i=0; i<size; i++) {
                        result.add(l1.get(i) + l2.get(i));
                }
                
                return result;
        }
        
        public static void showMatrix(LinkedList<Integer> l) {
                for(int i=0; i<3; i++) {
                        for(int j=0; j<3; j++) {
                                System.out.printf("%3d", l.get(i * 3 + j));
                        }
                        System.out.println();
                }
                System.out.println();
        }
        
        public static void main(String[] args) {
                LinkedList<Integer> mat1 = readMatrix("mat1.txt");
                LinkedList<Integer> mat2 = readMatrix("mat2.txt");
                
                System.out.println("Matrix 1:");
                showMatrix(mat1);
                System.out.println("Matrix 2:");
                showMatrix(mat2);
                
                System.out.println("Addition: ");
                showMatrix(addMatrices(mat1, mat2));
        }

}

mat1.txt:
2 6 2
6 2 18
17 11 20

mat2.txt:
3 13 5
4 11 20
13 18 20

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