Java 8 has String.join() method where first parameter is separator and then you can pass either multiple strings or some instance of Iterable having instances of strings as second parameter. Here is the sample program:

package in.mallikatalksjava.java8;
import java.time.ZoneId;

public class StringJoinDemo {
   public static void main(String[] args) {
	String joined = String.join("", "mallik", "talks", "java",".in");
	System.out.println(joined);
		
	String directory = String.join("/", "C:", "java", "programs");
	System.out.println(directory);

	String ids = String.join(", ", ZoneId.getAvailableZoneIds());
	System.out.println(ids);
	}
}

Output:
malliktalksjava.in
C:/java/programs
Asia/Aden, America/Cuiaba, Etc/GMT+9, Etc/GMT+8, Africa/Nairobi, America/Marigot, Asia/Aqtau ....etc.