### Question:
ColumnVector { @Override public String toString() { final DecimalFormat format = FormatUtils.getDefaultDecimalFormat(); final StringBuilder builder = new StringBuilder(); for (int i = 0; i < this.size; ++i) { if (0 != i) { builder.append(" "); } builder.append(format.format(this.vector[i])); } return builder.toString(); } ColumnVector(final int size);  ColumnVector(final double... vector); private  ColumnVector(final Matrix matrix); int size(); double getAt(final int index); void setAt(final int index, final double val); void incrementAt(final int index, final double val); void normalize(); void scale(final double scale); ColumnVector multiplyElementWise(final ColumnVector vector); ColumnVector addElementWise(final ColumnVector vector); double absSum(); double sum(); ColumnVector roundTo(final int numPlaces); ColumnVector add(final double scalar); ColumnVector multiply(final double scalar); ColumnVector sqrt(); ColumnVector abs(); final boolean isZeroVector(); double[] getRaw(); void setAll(final double val); boolean align(); double max(); double median(); double getMagnitude(); double l1Distance(final ColumnVector vector); double l2Distance(final ColumnVector vector); double correlation(final ColumnVector vector); @Override String toString(); void removeNegatives(); @Override int hashCode(); @Override boolean equals(final Object obj);  }### Answer:
@Test public void vectorStringRepresentationIsCorrect() { final ColumnVector vector = new ColumnVector(2.1234, 3.2345, 5012.0126, 11.1234, 1, 8); final String expectedResult = "2.123 3.235 5012.013 11.123 1.000 8.000"; MatcherAssert.assertThat(vector.toString(), IsEqual.equalTo(expectedResult)); }