Convert List of Object into single Map in Java

Convert List of Object into single Map in Java

Example: Let we have a List of Object in java and we want to convert it into a single map based on two fields of each object as key and value pair. 

Input:  [{"name":"Rocky","age":23,"employeecode":1},{"name":"Aman","age":21,"employeecode":2},{"name":"Sam","age":19,"employeecode":4},{"name":"Peter","age":23,"employeecode":3}]

Output: {Rocky=23, Aman=21, Peter=23, Sam=19}

Approach-1 Using Java 8 stream API

Java

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
public class Employee {
    
    private String name;
    
    private Integer age;
    
    private Integer employeecode;
    //getters setters
}
public class BecomeCodeExpert {
    public static void main(String[] args) {
        Employee emp1 = new Employee();
        emp1.setName("Aman");
        emp1.setEmployeecode(1);
        emp1.setAge(21);
        Employee emp2 = new Employee();
        emp2.setName("Sam");
        emp2.setEmployeecode(2);
        emp2.setAge(19);
        Employee emp3 = new Employee();
        emp3.setName("Peter");
        emp3.setEmployeecode(3);
        emp3.setAge(23);
        Employee emp4 = new Employee();
        emp4.setName("Rocky");
        emp4.setEmployeecode(4);
        emp4.setAge(23);
        
        // This is the List of Employee Class that we have to 
        // transform into Single Map
        List<Employee> employeeList = new ArrayList<>();
        employeeList.add(emp1);
        employeeList.add(emp2);
        employeeList.add(emp3);
        employeeList.add(emp4);
        System.out.println(employeeList);
        //code to convert List of object into single map
        Map<String, Integer> emplMap = employeeList.stream()
                .collect(Collectors.toMap(Employee::getName, Employee::getAge));
        System.out.println(emplMap);
    }
}

Approach-2 Using for loop

Java

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
public class BecomeCodeExpert {
    public static void main(String[] args) {
        Employee emp1 = new Employee();
        emp1.setName("Aman");
        emp1.setEmployeecode(1);
        emp1.setAge(21);
        Employee emp2 = new Employee();
        emp2.setName("Sam");
        emp2.setEmployeecode(2);
        emp2.setAge(19);
        Employee emp3 = new Employee();
        emp3.setName("Peter");
        emp3.setEmployeecode(3);
        emp3.setAge(23);
        Employee emp4 = new Employee();
        emp4.setName("Rocky");
        emp4.setEmployeecode(4);
        emp4.setAge(23);
        
        // This is the List of Employee Class that we have to
        // transform into Single Map
        List<Employee> employeeList = new ArrayList<>();
        employeeList.add(emp1);
        employeeList.add(emp2);
        employeeList.add(emp3);
        employeeList.add(emp4);
        //code to convert List of object into single map
        Map<String, Integer> emplMap = new HashMap<>();
        for(Employee employee:employeeList) {
            emplMap.put(employee.getName(), employee.getAge());
        }
        System.out.println(emplMap);
    }
}