MapToList.java

import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

public class ListToMap {

	public static void main(String[] args) {

		Transaction t1 = new Transaction("Submission", 1233L, "Initiated", "Failed");
		Transaction t2 = new Transaction("Submission", 1233L, "Quoted", "Passed");
		Transaction t3 = new Transaction("Submission", 1233L, "Submitted", "Passed");
		Transaction t4 = new Transaction("Renewal", 1366L, "Initiated", "Passed");
		Transaction t5 = new Transaction("Renewal", 1366L, "Quoted", "Failed");
		
		List<Transaction> trainsactions = Arrays.asList(t1, t2, t3, t4, t5);
		
		Map<Long,List<Event>> eventsbyTransaction = trainsactions.stream()
				.collect(Collectors.groupingBy(Transaction::getNumber, 
								Collectors.mapping( t-> 
										new Event(t.getType(), 
										t.getEventName(), 
										t.getStatus()),Collectors.toList())));
		
		System.out.println("Result : " + eventsbyTransaction);

	}

}


class Transaction {
	String type;
	Long number;
	String eventName;
	String status;
	public Transaction(String type, Long number, String eventName, String status) {
		super();
		this.type = type;
		this.number = number;
		this.eventName = eventName;
		this.status = status;
	}
	public String getType() {
		return type;
	}
	public void setType(String type) {
		this.type = type;
	}
	public Long getNumber() {
		return number;
	}
	public void setNumber(Long number) {
		this.number = number;
	}
	public String getEventName() {
		return eventName;
	}
	public void setEventName(String eventName) {
		this.eventName = eventName;
	}
	public String getStatus() {
		return status;
	}
	public void setStatus(String status) {
		this.status = status;
	}
}

class Event {
	
	String type;
	String eventName;
	String status;
	public Event(String type, String eventName, String status) {
		super();
		this.type = type;
		this.eventName = eventName;
		this.status = status;
	}
	public String getType() {
		return type;
	}
	public void setType(String type) {
		this.type = type;
	}
	public String getEventName() {
		return eventName;
	}
	public void setEventName(String eventName) {
		this.eventName = eventName;
	}
	public String getStatus() {
		return status;
	}
	public void setStatus(String status) {
		this.status = status;
	}
	@Override
	public String toString() {
		return "Event [type=" + type + ", eventName=" + eventName + ", status=" + status + "]";
	}
}