### Question:
ExtensibleMetaDataMapping { public String getColumnNameFromIndex(final String index) { String columnName = null; String foundIntValue = ""; for (String key : extensibleMappings.keySet()) { foundIntValue = extensibleMappings.get(key); if (foundIntValue.equals(index)) { columnName = key; break; } } return columnName; } 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 testGetColumnNameFromIndex() 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 actual = metaDataMapping.getColumnNameFromIndex(val1); Assert.assertEquals(key1, actual); }