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Author: basahota

java8/Employee.java

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+package com.java8;
+
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import java.util.List;
+
+@Data
+@AllArgsConstructor
+@NoArgsConstructor
+@Builder
+class Employee{
+	
+	private int id;
+	private String name;
+	private String dept;
+	private List<Project> projects;
+	private double salary;
+	private String gender;
+
+}
+

java8/EmployeeDataBase.java

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+package com.java8;
+
+import java.util.Arrays;
+import java.util.List;
+
+public class EmployeeDataBase {
+
+    public static List<Employee> getAllEmployees() {
+        Project p1 = new Project("P001", "Alpha", "ABC Corp", "Alice");
+        Project p2 = new Project("P002", "Beta", "XYZ Ltd", "Bob");
+        Project p3 = new Project("P003", "Gamma", "ABC Corp", "Alice");
+        Project p4 = new Project("P004", "Delta", "TechWorld", "Charlie");
+        Project p5 = new Project("P005", "Epsilon", "MoneyMatters", "Daniel");
+        Project p6 = new Project("P006", "Zeta", "SmartTech", "Eva");
+        Project p7 = new Project("P007", "Eta", "BrandBoost", "George");
+        Project p8 = new Project("P008", "Theta", "InnoSoft", "Hannah");
+        Project p9 = new Project("P009", "Iota", "FastTrack", "Ian");
+        Project p10 = new Project("P010", "Kappa", "DigitalWave", "Jessica");
+
+        // Employee instances
+        Employee e1 = new Employee(1, "John Doe", "Development", Arrays.asList(p1, p2), 80000, "Male");
+        Employee e2 = new Employee(2, "Jane Smith", "Development", Arrays.asList(p3), 80000, "Female");
+        Employee e3 = new Employee(3, "Robert Brown", "Sales", Arrays.asList(p4), 60000, "Male");
+        Employee e4 = new Employee(4, "Lisa White", "HR", Arrays.asList(p1), 55000, "Female");
+        Employee e5 = new Employee(5, "Michael Green", "Finance", Arrays.asList(p5), 90000, "Male");
+        Employee e6 = new Employee(6, "Sophia Brown", "Development", Arrays.asList(p6), 85000, "Female");
+        Employee e7 = new Employee(7, "James Wilson", "Marketing", Arrays.asList(p7), 72000, "Male");
+        Employee e8 = new Employee(8, "Olivia Harris", "Development", Arrays.asList(p8), 88000, "Female");
+        Employee e9 = new Employee(9, "William Lee", "Sales", Arrays.asList(p9), 78000, "Male");
+        Employee e10 = new Employee(10, "Emily Clark", "Development", Arrays.asList(p10), 95000, "Female");
+
+        // Print employee details (just for testing)
+        return Arrays.asList(e1, e2, e3, e4, e5, e6, e7, e8, e9, e10);
+    }
+}

java8/Java8MethodCheatSheet.java

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+package com.java8;
+
+import java.util.*;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+public class Java8MethodCheatSheet {
+
+    public static void main(String[] args) {
+
+
+        List<Employee> employees = EmployeeDataBase.getAllEmployees();
+
+      // forEach
+        //employees.forEach(e-> System.out.println(e.getName()+" : "+e.getSalary()));
+
+        //employees.stream().forEach(System.out::println);
+
+        //filter
+        //.collect
+
+        Map<Integer, String> developmentEmployees = employees.stream()
+                .filter(e -> e.getDept().equals("Development") && e.getSalary() > 80000)
+                .collect(Collectors.toMap(Employee::getId, Employee::getName));
+
+       // System.out.println(developmentEmployees);
+
+        //map
+        //distinct
+        List<String> depts = employees.stream()
+                .map(Employee::getDept)
+                .distinct()
+                .collect(Collectors.toList());
+        //System.out.println(depts);
+
+        List<Stream<String>> projectNames = employees.stream()
+                .map(e -> e.getProjects()
+                        .stream().map(p -> p.getName())).collect(Collectors.toList());
+
+        //flatMap
+
+        List<String> projects = employees.stream()
+                .flatMap(e -> e.getProjects().stream())
+                .map(p -> p.getName()).distinct()
+                .collect(Collectors.toList());
+
+        //System.out.println(projects);
+
+
+        //sorted
+        //asc
+        List<Employee> ascSortedEmployees = employees.stream()
+                .sorted(Comparator.comparing(Employee::getSalary))
+                .collect(Collectors.toList());
+
+//        ascSortedEmployees.get(0);
+
+        //ascSortedEmployees.forEach(System.out::println);
+
+        //desc
+        List<Employee> descSortedEmployees = employees.stream()
+                .sorted(Collections.reverseOrder(Comparator.comparing(Employee::getSalary)))
+                .collect(Collectors.toList());
+
+//        descSortedEmployees.get(0);
+
+        //descSortedEmployees.forEach(System.out::println);
+
+        //min & max
+        Optional<Employee> highestPaidEmployees = employees.stream()
+                .max(Comparator.comparingDouble(Employee::getSalary));
+
+       // System.out.println("Highest paid employee : "+highestPaidEmployees);
+
+        Optional<Employee> lowestPaidEmployees = employees.stream()
+                .min(Comparator.comparingDouble(Employee::getSalary));
+
+        //System.out.println("Lowest paid employee : "+lowestPaidEmployees);
+
+        //groupingBy
+
+        Map<String, List<Employee>> employeeGroup = employees.stream()
+                .collect(Collectors.groupingBy(Employee::getGender));
+
+        //System.out.println(employeeGroup);
+
+        //Gender -> [names]
+        Map<String, List<String>> employeeGroupNames = employees.stream()
+                .collect(Collectors.groupingBy(Employee::getGender,
+                        Collectors.mapping(Employee::getName, Collectors.toList())
+                ));
+
+        //System.out.println(employeeGroupNames);
+
+        //Gender -> [count]
+        Map<String, Long> employeeGroupCountMap = employees.stream()
+                .collect(Collectors.groupingBy(Employee::getGender, Collectors.counting()));
+        System.out.println(employeeGroupCountMap);
+
+        //findFirst
+
+        Employee findFirstElement = employees.stream()
+                .filter(e -> e.getDept().equals("Development"))
+                .findFirst()
+                .orElseThrow(()->new IllegalArgumentException("Employee not found "));
+
+//        System.out.println(findFirstElement.get());//NPE
+//
+//        if(findFirstElement.isPresent()){
+//            System.out.println(findFirstElement.get());
+//        }
+//
+//        findFirstElement.ifPresent(e-> System.out.println(e.getName()));
+
+        //System.out.println(findFirstElement);
+
+        //findAny
+
+        Employee findAnyElement = employees.stream()
+                .filter(e -> e.getDept().equals("Development"))
+                .findAny()
+                .orElseThrow(()->new IllegalArgumentException("Employee not found "));
+
+       // System.out.println(findAnyElement);
+
+        //anyMatch(Predicate) , allMatch(Predicate) , noneMatch(Predicate)
+
+        boolean developmentEmpAnyMatch = employees.stream()
+                .anyMatch(e -> e.getDept().equals("Development"));
+        //System.out.println("is there any employee match from development dept "+developmentEmpAnyMatch);
+
+
+        boolean developmentEmpAllMatch = employees.stream()
+                .allMatch(e -> e.getSalary()>50000);//55000
+        //System.out.println(developmentEmpAllMatch); //false
+
+
+        boolean isNoneMatch = employees.stream()
+                .noneMatch(e -> e.getDept().equals("abc"));
+        //System.out.println(isNoneMatch);
+
+        //limit(long)
+
+        List<Employee> topPaidEmployees = employees.stream()
+                .sorted(Comparator.comparing(Employee::getSalary).reversed())
+                .limit(4)
+                .collect(Collectors.toList());
+
+        topPaidEmployees.forEach(e-> System.out.println(e.getName()));
+
+        //skip(long)
+        List<Employee> skipEmployees = employees.stream().skip(10)
+                .collect(Collectors.toList());
+
+
+//
+//        forEach(Consumer)
+//        filter(Predicate)
+//        collect(Collector)
+//        map(Function)
+//        distinct()
+//        flatMap(Function)
+//        sorted(Comparator both ASC and DESC)
+//        min() & max()
+//        GroupBy
+//        findFirst()
+//        findAny()
+//        anyMatch(Predicate)
+//        allMatch(Predicate)
+//        noneMatch(Predicate)
+//        limit(long maxSize)
+//        skip(long n)
+
+
+    }
+}

java8/Project.java

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+package com.java8;
+
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+@Data
+@AllArgsConstructor
+@NoArgsConstructor
+@Builder
+class Project{
+
+	private String projectCode;
+	private String name ;
+	private String client;
+	private String buLeadName;
+}