Java join arraylist items into string

/**
 * @author lautturi.com
 * Java example: join arraylist items into string in java
 */

import java.util.*;
import java.time.*;

public class Lautturi {
	public static void main(String[] args) {
		ArrayList<String> al = new ArrayList<String>();
		al.add("Hello");
		al.add("lautturi");
		al.add("java");
		al.add("world");
		StringBuffer sb = new StringBuffer();

		for (String s : al) {
			sb.append(s);
			sb.append(" ");
		}
		String str = sb.toString();
		System.out.println(str);
	}
}

output:

Hello lautturi java world