Map m = new Map(); // Define a new map
m.put(1, 'First entry');                  // Insert a new key-value pair in the map
m.put(2, 'Second entry');                  // Insert a new key-value pair in the map
System.assert(m.containsKey(1));  // Assert that the map contains a key
String value = m.get(2);               // Retrieve a value, given a particular key
System.assertEquals('Second entry', value);
Set s = m.keySet();