How to represent a 2D matrix in Java? -

i have create in java 2d matrix (consisting of double values) 1d vector. should possible access individual rows , columns individual elements. moreover, should thread-safe (threads writing @ same time). perhaps later need matrix operations too.

which data structure best this? 2d array or treemap? or there amazing external library?

you should use vector 2d array. 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 matrix indexes

00 01

10 11

you can specifix index value this

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

have @ vector