### Question:
ExtensibleMetaDataMapping { public String getIndexFromColumnName(final String columnName) { String index = extensibleMappings.get(columnName); return index; } private  ExtensibleMetaDataMapping(final Map<String, String> extensibleMappings); synchronized static ExtensibleMetaDataMapping instance(final Map<String, String> extensibleMappings); String getIndexFromColumnName(final String columnName); String getColumnNameFromIndex(final String index);  }### Answer:
@Test public final void testGetIndexFromColumnName() throws Exception { Map<String, String> metaDataSource = new HashMap<String, String>(); String key1 = "key1"; String val1 = "10003"; String key2 = "key2"; String val2 = "10004"; metaDataSource.put(key1, val1); metaDataSource.put(key2, val2); ExtensibleMetaDataMapping metaDataMapping = ExtensibleMetaDataMapping.instance(metaDataSource); String index = metaDataMapping.getIndexFromColumnName(key1); Assert.assertEquals(val1, index); }