Question

### Functional Interfaces and Lambda Expressions
------------------------------------------------
Use the below class

public class LambdaSample {

    private static List<String> names=new ArrayList<>();
    private static Map<String,String> studentDetails;
    
    static {
        
    names=Arrays.asList( "Anju","Raju","Arun","Vikram");

        studentDetails=new HashMap<String,String>();
        studentDetails.put("Anju","Delhi");
        studentDetails.put("Raju","Chennai");
        studentDetails.put("Arun","Delhi");
        }
    

         }

Implement below static methods and access them from main method . Use Java8 functions

1. displayNames()
    --should displayall the names   

2. findByName(String name)
     -- check whether the given name exists in the list

3. getAllcount()
       -- count the number of person whose name starts with "A"

4. getStduentData()
   -- use biconsumer and print the student details

5. showMaxlength()
    -- display the list of names which is length to be 4 characters

Answer 1

import java.util.*;

public class LambdaSample {
    private static List<String> names = new ArrayList<>();
    private static Map<String, String> studentDetails;

    static {
        names = Arrays.asList("Anju", "Raju", "Arun", "Vikram");

        studentDetails = new HashMap<String, String>();
        studentDetails.put("Anju", "Delhi");
        studentDetails.put("Raju", "Chennai");
        studentDetails.put("Arun", "Delhi");
    }

    // --should displayall the names
    public static void displayNames() {
        names.forEach(System.out::println);
    }


    //-- check whether the given name exists in the list
    public static boolean findByName(String name) {
        return names.stream().anyMatch(nameS -> nameS.equals(name));
    }


    //-- count the number of person whose name starts with "A"
    public static long getAllCount() {
        return studentDetails.entrySet().stream()
                .filter(entry -> entry.getKey().startsWith("A"))
                .count();
    }


    //-- use biconsumer and print the student details
    public static void getStudentData() {
        studentDetails.forEach((s, s2) -> System.out.println(s + " " + s2));
    }


    // -- display the list of names which is length to be 4 characters
    public static void showMaxLength() {
        names.stream()
                .filter(name -> name.length() == 4)
                .forEach(System.out::println);
    }

}

public class Main {
    public static void main(String[] args) {
        LambdaSample.displayNames();
        System.out.println(LambdaSample.findByName("Arun"));
        System.out.println(LambdaSample.getAllCount());
        LambdaSample.getStudentData();
        LambdaSample.showMaxLength();
    }
}