Java.util.StringJoiner in Java 8 Example

Java.util.StringJoiner in Java 8 Example

Ans:I hope everybody knows about it.i am just giving my inputs on it.So

StringJoiner is a class in java.util package which is used to construct a sequence of characters(strings) separated by a delimiter and optionally starting with a supplied prefix and ending with a supplied suffix.
Though, this can also be with the help of StringBuilder class to append delimiter after each string, but StringJoiner provides easy way to do that without much code to write.

Constructors of StringJoiner :

1)StringJoiner(CharSequence delimiter) : 

Small description of it.

Syntax :

public StringJoiner(CharSequence delimiter)
Parameters :
delimiter - the sequence of characters to be used between
each element added to the StringJoiner value

Throws:
NullPointerException - if delimiter is null

2)StringJoiner(CharSequence delimiter,CharSequence prefix,CharSequence suffix) : 

Syntax :

public StringJoiner(CharSequence delimiter,
       CharSequence prefix, CharSequence suffix)
 
Parameters :
delimiter - the sequence of characters to be used between
each element added to the StringJoiner value
prefix - the sequence of characters to be used at the beginning
suffix - the sequence of characters to be used at the end

Throws:
NullPointerException - if prefix, delimiter, or suffix is null

Methods : There are 5 methods in StringJoiner class.

1)String toString() : 

Syntax :

public String toString()
Parameters :
NA
Returns :
the string representation of this StringJoiner
Overrides :
toString in class Object

2)StringJoiner add(CharSequence newElement) :

Syntax :
public StringJoiner add(CharSequence newElement)
Parameters :
newElement - The element to add
Returns :
a reference to this StringJoiner

3)StringJoiner merge(StringJoiner other) :

Syntax :
public StringJoiner merge(StringJoiner other)
Parameters :
other - The StringJoiner whose contents should be merged
into this one
Returns :
This StringJoiner
Throws :
NullPointerException - if the other StringJoiner is null

4)int length() : 

Syntax :
public int length()
Parameters :
NA
Returns :
This StringJoiner

5)StringJoiner setEmptyValue(CharSequence emptyValue) :

Syntax :
public StringJoiner setEmptyValue(CharSequence emptyValue)
Parameters :
emptyValue - the characters to return as the value
of an empty StringJoiner
Returns :
this StringJoiner itself so the calls may be chained
Throws:
NullPointerException - when the emptyValue parameter is null

Sample Program for StringJoiner:

import java.util.ArrayList;
import java.util.StringJoiner;

public class SampleProgram
{
public static void main(String[] args)
{
ArrayList<String> al = new ArrayList<>();

al.add("Abhinaw");
al.add("Abhishek");
al.add("Ram");
al.add("VirtualRelaity");

StringJoiner sj1 = new StringJoiner(",");

// setEmptyValue() method
sj1.setEmptyValue("sj1 is empty");
System.out.println(sj1);

// add() method
sj1.add(al.get(0)).add(al.get(1));
System.out.println(sj1);

// length() method
System.out.println("Length of sj1 : " + sj1.length());

StringJoiner sj2 = new StringJoiner(":");
sj2.add(al.get(2)).add(al.get(3));

//merge() method
sj1.merge(sj2);

// toString() method
System.out.println(sj1.toString());

System.out.println("Length of new sj1 : " + sj1.length());

}
}

Output:

sj1 is empty
Abhinaw,Abhishek
Length of sj1 : 16
Abhinaw,Abhishek,Ram:VirtualRelaity
Length of new sj1 : 35