Java added a new final class StringJoiner in java.util package. It is used to construct a sequence of characters separated by a delimiter. Now, you can create string by passing delimiters like comma(,), hyphen(-) etc. You can also pass prefix and suffix to the char sequence.

Table of Contents

StringJoiner Constructors

Constructor	Description
Public StringJoiner(CharSequence delimiter)	It constructs a StringJoiner with no characters in it, with no prefix or suffix, and a copy of the supplied delimiter. It throws NullPointerException if delimiter is null.
Public StringJoiner(CharSequence delimiter,CharSequence prefix,CharSequence suffix)	It constructs a StringJoiner with no characters in it using copies of the supplied prefix, delimiter and suffix. It throws NullPointerException if prefix, delimiter, or suffix is null.

StringJoiner Methods

Method	Description
Public StringJoiner add(CharSequence newElement)	It adds a copy of the given CharSequence value as the next element of the StringJoiner value. If newElement is null,”null” is added.
Public StringJoiner merge(StringJoiner other)	It adds the contents of the given StringJoiner without prefix and suffix as the next element if it is non-empty. If the given StringJoiner is empty, the call has no effect.
Public int length()	It returns the length of the String representation of this StringJoiner.
Public StringJoiner setEmptyValue(CharSequence emptyValue)	It sets the sequence of characters to be used when determining the string representation of this StringJoiner and no elements have been added yet, that is, when it is empty.

Java StringJoiner Example

1. // importing StringJoiner class 
2. import java.util.StringJoiner; 
3. public class StringJoinerExample { 
4. public static void main(String[] args) { 
5. StringJoiner joinNames = new StringJoiner(","); // passing comma(,) as delimiter 
6. 
7. // Adding values to StringJoiner 
8. joinNames.add("Rahul"); 
9. joinNames.add("Raju"); 
10. joinNames.add("Peter"); 
11. joinNames.add("Raheem"); 
12. 
13. System.out.println(joinNames); 
14. } 
15. }

Output:
Rahul,Raju,Peter,Raheem

Java StringJoiner Example: adding prefix and suffix

1. // importing StringJoiner class 
2. import java.util.StringJoiner; 
3. public class StringJoinerExample { 
4. public static void main(String[] args) { 
5. StringJoiner joinNames = new StringJoiner(",", "[", "]"); // passing comma(,) and square-brackets as delimiter 
6. 
7. // Adding values to StringJoiner 
8. joinNames.add("Rahul"); 
9. joinNames.add("Raju"); 
10. joinNames.add("Peter"); 
11. joinNames.add("Raheem"); 
12. 
13. System.out.println(joinNames); 
14. } 
15. }

Output:
[Rahul,Raju,Peter,Raheem]

StringJoiner Example: Merge Two StringJoiner

The merge() method merges two StringJoiner objects excluding of prefix and suffix of second StringJoiner object.

1. // importing StringJoiner class 
2. import java.util.StringJoiner; 
3. public class StringJoinerExample { 
4. public static void main(String[] args) { 
5. 
6. StringJoiner joinNames = new StringJoiner(",", "[", "]"); // passing comma(,) and square-brackets as delimiter 
7. 
8. // Adding values to StringJoiner 
9. joinNames.add("Rahul"); 
10. joinNames.add("Raju"); 
11. 
12. // Creating StringJoiner with :(colon) delimiter 
13. StringJoiner joinNames2 = new StringJoiner(":", "[", "]"); // passing colon(:) and square-brackets as delimiter 
14. 
15. // Adding values to StringJoiner 
16. joinNames2.add("Peter"); 
17. joinNames2.add("Raheem"); 
18. 
19. // Merging two StringJoiner 
20. StringJoiner merge = joinNames.merge(joinNames2); 
21. System.out.println(merge); 
22. } 
23. }

Output:
[Rahul,Raju,Peter:Raheem]

StringJoiner Example: StringJoiner Methods

1. // importing StringJoiner class 
2. import java.util.StringJoiner; 
3. public class StringJoinerExample { 
4. public static void main(String[] args) { 
5. StringJoiner joinNames = new StringJoiner(","); // passing comma(,) as delimiter 
6. 
7. // Prints nothing because it is empty 
8. System.out.println(joinNames); 
9. 
10. // We can set default empty value. 
11. joinNames.setEmptyValue("It is empty"); 
12. System.out.println(joinNames); 
13. 
14. 
15. // Adding values to StringJoiner 
16. joinNames.add("Rahul"); 
17. joinNames.add("Raju"); 
18. System.out.println(joinNames); 
19. 
20. // Returns length of StringJoiner 
21. int length = joinNames.length(); 
22. System.out.println("Length: "+length); 
23. 
24. // Returns StringJoiner as String type 
25. String str = joinNames.toString(); 
26. System.out.println(str); 
27. 
28. // Now, we can apply String methods on it 
29. char ch = str.charAt(3); 
30. System.out.println("Character at index 3: "+ch); 
31. 
32. // Adding one more element 
33. joinNames.add("Sorabh"); 
34. System.out.println(joinNames); 
35. 
36. // Returns length 
37. int newLength = joinNames.length(); 
38. System.out.println("New Length: "+newLength); 
39. } 
40. }

Output:

It is empty
Rahul,Raju
Length: 10
Rahul,Raju
Character at index 3: u
Rahul,Raju,Sorabh
New Length: 17

Difference between ArrayList and Vector

ArrayList and Vector both implements List interface and maintains insertion order.
However, there are many differences between ArrayList and Vector classes that are given below.

ArrayList	Vector
1) ArrayList is not synchronized.	Vector is synchronized.
2) ArrayList increments 50% of current array size if the number of elements exceeds from its capacity.	Vector increments 100% means doubles the array size if the total number of elements exceeds than its capacity.
3) ArrayList is not a legacy class. It is introduced in JDK 1.2.	Vector is a legacy class.
4) ArrayList is fast because it is non-synchronized.	Vector is slow because it is synchronized, i.e., in a multithreading environment, it holds the other threads in runnable or non-runnable state until current thread releases the lock of the object.
5) ArrayList uses the Iterator interface to traverse the elements.	A Vector can use the Iterator interface or Enumeration interface to traverse the elements.

java 87

Example of Java ArrayList

Let’s see a simple example where we are using ArrayList to store and traverse the elements.

1. import java.util.*; 
2. class TestArrayList21{ 
3. public static void main(String args[]){ 
4. 
5. List<String> al=new ArrayList<String>();//creating arraylist 
6. al.add("Sonoo");//adding object in arraylist 
7. al.add("Michael"); 
8. al.add("James"); 
9. al.add("Andy"); 
10. //traversing elements using Iterator 
11. Iterator itr=al.iterator(); 
12. while(itr.hasNext()){ 
13. System.out.println(itr.next()); 
14. } 
15. } 
16. }

Test it Now
Output:
Sonoo
Michael
James
Andy

Example of Java Vector

Let’s see a simple example of a Java Vector class that uses the Enumeration interface.

1. import java.util.*; 
2. class TestVector1{ 
3. public static void main(String args[]){ 
4. Vector<String> v=new Vector<String>();//creating vector 
5. v.add("umesh");//method of Collection 
6. v.addElement("irfan");//method of Vector 
7. v.addElement("kumar"); 
8. //traversing elements using Enumeration 
9. Enumeration e=v.elements(); 
10. while(e.hasMoreElements()){ 
11. System.out.println(e.nextElement()); 
12. } 
13. } 
14. }

Output:
umesh
irfan
kumar

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