Is there a way to make a string from ArrayList elements?

I want to ask the user for a message:

> "Enter a message in the following format: "TO FROM MESSAGE : KEY"

Example input from user:

> 1 2 hey there how are you : bubble123

Then, I want to have the SecureMessage class return the message. However, I do not know how to create a String of the message part, as the getMessage() message requires a String assigned to it.

The SecureMessage class should not have any mutators in it. All fields in SecureMessage are set from the Message class.

public class SecureMessage {
private String message;
private String sourceName;
private String destName;
private String key;
public SecureMessage(String message, String sourceName, String destName, String key){
this.message = message;
this.sourceName = sourceName;
this.destName = destName;
this.key = key;
}
public String getMessage(String key){ 
return message + " from SecureMessage class";
}
public String getSourceName(){
return sourceName + " from SecureMessage class";
}
public String getDestName(){
return destName + " from SecureMessage class";
}
}

import java.util.ArrayList;
import java.util.Scanner;
public class Message {
public static void main(String[] args) {
Scanner keyboard = new Scanner(System.in);
String message = "blank", sourceName = "blank", destName = "blank", key = "blank", messageInput, userMessageDetails;
ArrayList<String> messageInputList = new ArrayList<>();
System.out.println("Enter message in form TO FROM MESSAGE : KEY \nExample --- 1 2 hey there how are you? : bubble123");
userMessageDetails = keyboard.nextLine();
String str = userMessageDetails;
String[] tokens = str.split(" ");        
for(String s : tokens){
messageInputList.add(s);
}
System.out.println(messageInputList);
System.out.println("");
int x = messageInputList.size();
destName = messageInputList.get(0);
sourceName = messageInputList.get(1);
key = messageInputList.get(x-1);
//--this is where I am lost, because I need to pass a string to the SecureMessage getMessage() method---
//        message = ???;
// I found out how to print the items, however this is not a string...
//        for(int i = 2; i <= (x-3); i++){
//            System.out.print(messageInputList.get(i) + " ");
//        }
//------------------------------------------------------------------------------------------------------
SecureMessage secMsg = new SecureMessage(message, sourceName, destName, key);
System.out.println(secMsg.getDestName());
System.out.println(secMsg.getSourceName());
System.out.println(secMsg.getMessage(key));
}
}

This should do it:

message = String.join(" ", messageInputList.subList(2, x-2));

So for what I see, as you split by " ", then you will have your message split between messageInputList.get(2) and messageInputList.get(x-3).
The easy way is having a for and concatenate strings. Something like:

String s_message = "";
for(int i = 2; i <= (x-3); i++){
s_message = s_message + messageInputList.get(i) + " ";
}

message = IntStream.range(2, x - 2)
.mapToObj(messageInputList::get)
.collect(Collectors.joining(" "));

This will collect the elements from your messageInputList from index 2 to x-2 and collect them to a singular String message which you can pass to your SecureMessage class.

I think it could be much more simplier:

public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
System.out.println("Enter message data.");
System.out.println("-------------------");
System.out.print("Destination name: ");
String destName = scan.next();
System.out.print("Source name: ");
String sourceName = scan.next();
System.out.print("Key: ");
String key = scan.next();
System.out.println("Message (multi-line, double ENTER to finish):");
scan.useDelimiter("\n\n\n");
String message = scan.next().trim();
SecureMessage secMsg = new SecureMessage(message, sourceName, destName, key);
System.out.println(secMsg.getDestName());
System.out.println(secMsg.getSourceName());
System.out.println(secMsg.getMessage(key));
}