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@greekykhs

greekykhs/EmployeeStream.java

Last active June 26, 2020 14:28
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  1. greekykhs revised this gist Jun 26, 2020. 1 changed file with 7 additions and 0 deletions.
    7 changes: 7 additions & 0 deletions EmployeeStream.java
    View file
    Original file line number Diff line number Diff line change
    @@ -36,6 +36,13 @@ public static void main(String[] args) throws Exception{
    .filter(e->e.getSalary()<8000)
    .collect(Collectors.toList());

    //find top 3 highest earning employees
    employees.stream()
    .sorted(Comparator.comparingDouble(Employee::getSalary).reversed())
    .limit(3)
    .map(Employee::getName)
    .forEach(System.out::println);

    //Sort employees by age using method reference
    employees.stream()
    .sorted(Comparator.comparing(Employee::getAge))
  2. greekykhs revised this gist Jun 26, 2020. 1 changed file with 8 additions and 4 deletions.
    12 changes: 8 additions & 4 deletions EmployeeStream.java
    View file
    Original file line number Diff line number Diff line change
    @@ -21,7 +21,8 @@ public static void main(String[] args) throws Exception{

    //Sort employees based on Date of Joining
    employees.stream()
    .sorted((e1, e2)->e1.getDateOfJoining().compareTo(e2.getDateOfJoining()))
    .sorted((e1, e2)->e1.getDateOfJoining()
    .compareTo(e2.getDateOfJoining()))
    .collect(Collectors.toList());

    //Sort employees based on Date of Joining
    @@ -47,11 +48,13 @@ public static void main(String[] args) throws Exception{

    //Covert the list into map, where key:id, value:name
    Map<Integer, String> empMap=employees.stream()
    .collect(Collectors.toMap(e->e.getId(), e->e.getName()));
    .collect(Collectors.toMap
    (e->e.getId(), e->e.getName()));

    //Covert the list into map using method ref, where key:id, value:name
    empMap=employees.stream()
    .collect(Collectors.toMap(Employee::getId, Employee::getName));
    .collect(Collectors.toMap
    (Employee::getId, Employee::getName));

    //While converting to a map if the duplicate key is encountered
    //it will throw 'java.lang.IllegalStateException: Duplicate key'.
    @@ -90,7 +93,8 @@ public static void main(String[] args) throws Exception{
    .map(Employee::getName)
    .collect(Collectors.joining(", ", "{", "}"));

    //Divide the employees into groups according to salary is greater than 5000
    //Divide the employees into groups according to salary
    //is greater than 5000
    Map<Boolean, List<Employee>> mappedEmployees=employees.stream()
    .collect(Collectors.partitioningBy
    (e->e.getSalary()>5000));
  3. greekykhs created this gist Jun 20, 2020.
    123 changes: 123 additions & 0 deletions EmployeeStream.java
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,123 @@
    public static List<Employee> getEmployees() throws Exception {
    SimpleDateFormat dateformat = new SimpleDateFormat("dd/MM/yyyy");
    Date dateOfJoining1 = dateformat.parse("17/07/1989");
    Date dateOfJoining2 = dateformat.parse("15/10/2007");
    Date dateOfJoining3 = dateformat.parse("01/10/2020");
    Date dateOfJoining4 = dateformat.parse("11/11/2020");

    List<Employee> employees=new ArrayList<>();
    employees.add(new Employee(1, "Ronalda", 5000, dateOfJoining1, 28));
    employees.add(new Employee(2, "Matilda", 7000, dateOfJoining2, 32));
    employees.add(new Employee(3, "Roslie", 10000, dateOfJoining3, 50));
    employees.add(new Employee(4, "Martha", 55000, dateOfJoining4, 60));

    return employees;
    }
    public static void main(String[] args) throws Exception{
    List<Employee> employees=getEmployees();

    //count the number of employees
    long count=employees.stream().count();

    //Sort employees based on Date of Joining
    employees.stream()
    .sorted((e1, e2)->e1.getDateOfJoining().compareTo(e2.getDateOfJoining()))
    .collect(Collectors.toList());

    //Sort employees based on Date of Joining
    //using method reference
    employees.stream()
    .sorted(Comparator.comparing(Employee::getDateOfJoining))
    .collect(Collectors.toList());

    //Filter employees with salary less than 8000
    employees.stream()
    .filter(e->e.getSalary()<8000)
    .collect(Collectors.toList());

    //Sort employees by age using method reference
    employees.stream()
    .sorted(Comparator.comparing(Employee::getAge))
    .collect(Collectors.toList());

    //Sort employees by age in reverse order using method reference
    employees.stream()
    .sorted(Comparator.comparing(Employee::getAge).reversed())
    .collect(Collectors.toList());

    //Covert the list into map, where key:id, value:name
    Map<Integer, String> empMap=employees.stream()
    .collect(Collectors.toMap(e->e.getId(), e->e.getName()));

    //Covert the list into map using method ref, where key:id, value:name
    empMap=employees.stream()
    .collect(Collectors.toMap(Employee::getId, Employee::getName));

    //While converting to a map if the duplicate key is encountered
    //it will throw 'java.lang.IllegalStateException: Duplicate key'.
    //We can handle this by providing merging function.
    empMap=employees.stream()
    .collect(Collectors.toMap(e->e.getId(), e->e.getName(),
    (oldName, newName)->oldName+newName));

    //Print name of all the employees in captial letters in sorted order
    employees.stream()
    .map(e->e.getName())
    .map(String::toUpperCase)
    .sorted()
    .forEach(System.out::println);

    //Find average age of employee
    double averageAge=employees.stream()
    .mapToInt(e->e.getAge())
    .average().getAsDouble();
    //OR
    averageAge=employees.stream()
    .collect(Collectors.averagingDouble(e -> e.getAge()));

    //Print the max salary
    employees.stream()
    .mapToDouble(e->e.getSalary())
    .max()
    .ifPresent(System.out::println);

    //groups all Employees by age
    Map<Integer, List<Employee>> empAgeGroup=employees.stream()
    .collect(Collectors.groupingBy(e -> e.getAge()));

    //Convert employee names into a comma seperated string
    String commaSepratedNames = employees.stream()
    .map(Employee::getName)
    .collect(Collectors.joining(", ", "{", "}"));

    //Divide the employees into groups according to salary is greater than 5000
    Map<Boolean, List<Employee>> mappedEmployees=employees.stream()
    .collect(Collectors.partitioningBy
    (e->e.getSalary()>5000));

    //Increment the salary of each employee by 2000
    employees.stream()
    .peek(e -> e.setSalary(e.getSalary() + 2000))
    .peek(System.out::println)
    .collect(Collectors.toList());

    //Find the youngest and oldest employee
    Employee youngEmployee=employees.stream()
    .min((e1, e2)->e1.getAge() - e2.getAge())
    .orElseThrow(NoSuchElementException::new);
    Employee oldEmployee=employees.stream()
    .max(Comparator.comparing(Employee::getAge))
    .orElseThrow(NoSuchElementException::new);

    //Convert the list into Set of employee names
    Set<String> empNames = employees.stream()
    .map(Employee::getName)
    .collect(Collectors.toSet());

    //summaryStatistics()
    //statics.getMin(), statics.getMax(), statics.getAverage()
    //statics.getCount(), statics.getCount()
    DoubleSummaryStatistics statics = employees.stream()
    .mapToDouble(Employee::getSalary)
    .summaryStatistics();
    }