Java 8 - StringJoiner with examples

StringJoiner is used to construct a sequence of characters separated by a delimiter and optionally starting with a supplied prefix and ending with a supplied suffix. Internally StringJoiner uses the String.join()

Lets see simple examples with various uses of StringJoiner class.

• Joning string by delimiter
• Other way to join string with delimiter
• List to string
• Adding delimiter, prefix and suffix
• Using setEmptyValue() method
• Using setEmptyValue() method - Same after adding some value
• Merging 2 string joiner 

public class StringJoiners {

 public static void main(String[] args) {
  
  //Joning string by delimiter
  StringJoiner sj = new StringJoiner(",");
  sj.add("Java");
  sj.add("Discover");
  sj.add("2018");
  System.out.println("Joning string by delimiter :: "+ sj.toString());
  
  
  
  //Other way to join string with delimiter
  String str = String.join(",", "JAVA", "DISCOVER", "2018");
  System.out.println("\nOther way : "+str);
  
  
  //List to string
  List<String> list = Arrays.asList("Java", "String", "Joiner");
  String str1 = String.join(", ", list);
  System.out.println("\nList to string : "+str1);
  
  
  //Adding delimiter, prefix and suffix
  StringJoiner sj1 = new StringJoiner(".","Hello "," :)");
  sj1.add("Java");
  sj1.add("Discover");
  sj1.add("2018");
  System.out.println("\nAdding delimiter, prefix and suffix :: "+ sj1.toString());
  
  
  
  /*
   * Using setEmptyValue() method - set default value of the string
   * if string is empty
   */
  StringJoiner sj2 = new StringJoiner("*");   
  sj2.setEmptyValue("DEFUALT EMPTY STRING");
  System.out.println("\nUsing setEmptyValue() method-1 :: "+ sj2.toString() + " ---- LENGTH : "+sj2.toString().length());
  

  // Same after adding some value
  sj2.add("ORACLE");
  sj2.add("LAMBDA");
  System.out.println("\nUsing setEmptyValue() method-2 :: "+ sj2.toString() + " ---- LENGTH : "+sj2.toString().length());
  
  
  
  //Merging 2 string joiner 
  StringJoiner sj3 = sj1.merge(sj2);
  System.out.println("\nMerging 2 string joiner :: "+sj3.toString());
 }
}

OUTPUT:

Joning string by delimiter :: Java,Discover,2018

Other way : JAVA,DISCOVER,2018

List to string : Java, String, Joiner

Adding delimiter, prefix and suffix :: Hello Java.Discover.2018 :)

Using setEmptyValue() method-1 :: DEFUALT EMPTY STRING ---- LENGTH : 20

Using setEmptyValue() method-2 :: ORACLE*LAMBDA ---- LENGTH : 13

Merging 2 string joiner :: Hello Java.Discover.2018.ORACLE*LAMBDA :)