### Question:
SingleVersion implements Version { public static final SingleVersion valueOf(String version) { SingleVersion singleVersion = CACHE.get(version); if (singleVersion == null) { singleVersion = new SingleVersion(version); CACHE.put(version, singleVersion); } return singleVersion; } @Deprecated  SingleVersion(String version); static final SingleVersion valueOf(String version); @Override int hashCode(); @Override boolean equals(Object other); @Override int compareTo(Version otherVersion); @Override int getMajorVersion(); @Override int getMinorVersion(); @Override int getIncrementalVersion(); @Override int getBuildNumber(); @Override String getQualifier(); @Override String toString();  }### Answer:
@Test(expected = IllegalArgumentException.class) public void testVersionMustNotBeNull() { SingleVersion.valueOf(null); }