### Question:
DiVector { public static DiVector addToLeft(DiVector left, DiVector right) { checkNotNull(left, "left must not be null"); checkNotNull(right, "right must not be null"); checkArgument(left.dimensions == right.dimensions, "dimensions must be the same"); for (int i = 0; i < left.dimensions; i++) { left.high[i] += right.high[i]; left.low[i] += right.low[i]; } return left; } DiVector(int dimensions);  DiVector(DiVector base); static DiVector addToLeft(DiVector left, DiVector right); int getDimensions(); DiVector scale(double z); void renormalize(double targetNorm); void componentwiseTransform(Function<Double, Double> function); double getHighLowSum(int i); double getHighLowSum(); final double[] high; final double[] low; }### Answer:
@Test public void testAddToLeft() { DiVector left = new DiVector(dimensions); DiVector right = new DiVector(dimensions); for (int i = 0; i < dimensions; i++) { left.low[i] = Math.random(); left.high[i] = Math.random(); right.low[i] = Math.random(); right.high[i] = Math.random(); } DiVector leftCopy = new DiVector(dimensions); System.arraycopy(left.low, 0, leftCopy.low, 0, dimensions); System.arraycopy(left.high, 0, leftCopy.high, 0, dimensions); DiVector rightCopy = new DiVector(dimensions); System.arraycopy(right.low, 0, rightCopy.low, 0, dimensions); System.arraycopy(right.high, 0, rightCopy.high, 0, dimensions); DiVector result = DiVector.addToLeft(left, right); assertSame(result, left); assertArrayEquals(rightCopy.low, right.low); assertArrayEquals(rightCopy.high, right.high); for (int i = 0; i < dimensions; i++) { assertEquals(leftCopy.low[i] + right.low[i], left.low[i]); assertEquals(leftCopy.high[i] + right.high[i], left.high[i]); } }