JavaArray2D a = new JavaArray2D();
a.set(0, 0, 100);
a.set(2, 2, 300);
assertEquals(100.0, a.get(0, 0));
assertEquals(0, a.numColumns(1)); // row 1 has not been assigned anything
assertEquals(300.0, a.get(2, 2));
// Columns 0 and 1 not exlicitly assigned in this row; expects default value of 0.
assertEquals(0.0, a.get(2, 0));
assertEquals(0.0, a.get(2, 1));