The purpose is to create a NxM matrix from an array of strings, ex:

String[] arrayOfStrings = new String[] {"1 2 3","4 5 6"} 

Then the output matrix would be

Integer[][] matrix = new Integer[][] { {1,2,3},{4,5,6}} 

The transformer should be generic enough that it can produce a matrix of Double, Integer…

for 1 dimension I was able to do it. Here is the code:

   /**      * Construct a matrix row from string line      * Example:      * in  = "1.7 5.14 9"      * out = new Double[] { 1.7 ,5.14,9}      *      * @param in               string to lineToRow      * @param compatibleParser specialize parser      * @param <E>              type      * @return matrix row      */     public static <E> E[] lineToRow(String in, Function<String, E> compatibleParser) {         final String[] els = in.split(" +"); /* ignore multiple spaces */         final E[] res = (E[]) new Object[els.length];         int i = 0;         for (String s : els) {             res[i] = compatibleParser.apply(s);             i++;         }         return res;     } 

and the test for it is like following:

@Test     public void stringLineToMatrixRow() {          String line0 = "1 2 3";         Assert.assertArrayEquals(new Integer[]{1, 2, 3}, MatrixUtils.lineToRow(line0, Integer::parseInt));         Assert.assertArrayEquals(new Double[]{1.7, 2.99, 3.8}, MatrixUtils.lineToRow("1.7   2.99 3.8", Double::valueOf));     } 

For 2 dims my only success is by “hard coding” the type, see ex:

   /**      * TODO find a way to use something like E[][]      */     public static Double[][] lineToRow(String[] ins) {         int i = 0;         Double[][] res = new Double[ins.length][3];         for (String ss : ins) {             int j = 0;             final String[] els = ss.split(" +");             for (String s : els) {                 res[i][j] = Double.valueOf(s);                 j++;             }             i++;         }         return res;     } 

It works for 1 dim array because this line (from example 1) is ok:

final E[] res = (E[]) new Object[els.length]; **but not for E[][] ...**