def employeeSalary = ['John' : 3000, 'Mary' : 4500, 'Adam' : 1500, 'Melissa':2500]
employeeSalary.put('Neil', 6000)         
println employeeSalary           // [John:3000, Mary:4500, Adam:1500, Melissa:2500, Neil:6000]
println employeeSalary.containsKey('Mary')     // true
println employeeSalary.get('Adam', 5000)       // 1500
println employeeSalary.get('Sally',5000)       //5000
println employeeSalary.get('Adam')             // 1500
println employeeSalary.get('Sally')            //null
println employeeSalary.get('Melissa')          // 2500
println employeeSalary.keySet()                // [John, Mary, Adam, Melissa, Neil]
println employeeSalary.size()                  // 5
println employeeSalary['John']                 // 3000