CODEWITHSUNDEEP
javamatrixdata-structures
machinery
machinery

Reputation: 6290

How to represent a 2D matrix in Java?

I have to create in Java a 2D matrix (consisting of double values) as well as a 1D vector. It should be possible to access individual rows and columns as well as individual elements. Moreover, it should be thread-safe (threads writing at the same time). Perhaps later I need some matrix operations too.

Which data structure is best for this? Just a 2D array or a TreeMap? Or is there any amazing external library?

Upvotes: 11

Views: 57463

Answers (3)

Aniket Rangrej
Aniket Rangrej

Reputation: 192

If you need thread safe behavior, use 

Vector<Vector<Double>> matrix = new Vector<Vector<Double>>();

If you don't need thread safe behavior, use 

ArrayList<ArrayList<Double>> matrix = new ArrayList<ArrayList<Double>>();

Upvotes: 5

Noor Nawaz
Noor Nawaz

Reputation: 2225

You should use Vector for 2D array. It is threadsafe.

Vector<Vector<Double>>  matrix= new Vector<Vector<Double>>();

    for(int i=0;i<2;i++){
        Vector<Double> r=new Vector<>();
        for(int j=0;j<2;j++){
            r.add(Math.random());
        }
        matrix.add(r);
    }
    for(int i=0;i<2;i++){
        Vector<Double> r=matrix.get(i);
        for(int j=0;j<2;j++){
            System.out.print(r.get(j));
        }
        System.out.println();
    }

If this is your matrix indexes

00 01

10 11

You can get specifix index value like this

Double r2c1=matrix.get(1).get(0); //2nd row 1st column

Have a look at Vector

Upvotes: 10

Paulo
Paulo

Reputation: 1498

I'll give you an example:

int rowLen = 10, colLen = 20;   
Integer[][] matrix = new Integer[rowLen][colLen];
for(int i = 0; i < rowLen; i++)
    for(int j = 0; j < colLen; j++)
        matrix[i][j] = 2*(i + j); // only an example of how to access it. you can do here whatever you want.

Clear?

Upvotes: 13

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