ExampleVar.java

var employees = Arrays.asList(new Employee(1, "Ashish", 28, 10000)
                , new Employee(2, "Ajay", 29, 1000)
                , new Employee(3, "Abhishek", 29, 10000));
var employeeMap = employees.stream()
  .collect(Collectors.toMap(Employee::getId, Employee::getName));
var groupedMap = employees.stream()
  .collect(Collectors.groupingBy(Employee::getSalary));