### Question:
Hash { public int hash(byte[] bytes) { return hash(bytes, bytes.length, -1); }  static int parseHashType(String name); static int getHashType(Configuration conf); static Hash getInstance(int type); static Hash getInstance(Configuration conf); int hash(byte[] bytes); int hash(byte[] bytes, int initval); abstract int hash(byte[] bytes, int length, int initval); static final int INVALID_HASH; static final int JENKINS_HASH; static final int MURMUR_HASH; }### Answer:
@Test public void testHash() { int iterations = 30; assertTrue("testHash jenkins error !!!", Hash.JENKINS_HASH == Hash.parseHashType("jenkins")); assertTrue("testHash murmur error !!!", Hash.MURMUR_HASH == Hash.parseHashType("murmur")); assertTrue("testHash undefined", Hash.INVALID_HASH == Hash.parseHashType("undefined")); Configuration cfg = new Configuration(); cfg.set("hadoop.util.hash.type", "murmur"); assertTrue("testHash", MurmurHash.getInstance() == Hash.getInstance(cfg)); cfg = new Configuration(); cfg.set("hadoop.util.hash.type", "jenkins"); assertTrue("testHash jenkins configuration error !!!", JenkinsHash.getInstance() == Hash.getInstance(cfg)); cfg = new Configuration(); assertTrue("testHash undefine configuration error !!!", MurmurHash.getInstance() == Hash.getInstance(cfg)); assertTrue("testHash error jenkin getInstance !!!", JenkinsHash.getInstance() == Hash.getInstance(Hash.JENKINS_HASH)); assertTrue("testHash error murmur getInstance !!!", MurmurHash.getInstance() == Hash.getInstance(Hash.MURMUR_HASH)); assertNull("testHash error invalid getInstance !!!", Hash.getInstance(Hash.INVALID_HASH)); int murmurHash = Hash.getInstance(Hash.MURMUR_HASH).hash(LINE.getBytes()); for (int i = 0; i < iterations; i++) { assertTrue("multiple evaluation murmur hash error !!!", murmurHash == Hash.getInstance(Hash.MURMUR_HASH) .hash(LINE.getBytes())); } murmurHash = Hash.getInstance(Hash.MURMUR_HASH).hash(LINE.getBytes(), 67); for (int i = 0; i < iterations; i++) { assertTrue( "multiple evaluation murmur hash error !!!", murmurHash == Hash.getInstance(Hash.MURMUR_HASH).hash( LINE.getBytes(), 67)); } int jenkinsHash = Hash.getInstance(Hash.JENKINS_HASH).hash(LINE.getBytes()); for (int i = 0; i < iterations; i++) { assertTrue( "multiple evaluation jenkins hash error !!!", jenkinsHash == Hash.getInstance(Hash.JENKINS_HASH).hash( LINE.getBytes())); } jenkinsHash = Hash.getInstance(Hash.JENKINS_HASH).hash(LINE.getBytes(), 67); for (int i = 0; i < iterations; i++) { assertTrue( "multiple evaluation jenkins hash error !!!", jenkinsHash == Hash.getInstance(Hash.JENKINS_HASH).hash( LINE.getBytes(), 67)); } }