Java Stringjoiner Class
StringJoiner is a class which is used to construct a sequence of characters which are separated by a delimiter. Optionally, it starts with a provided prefix and ended with the provided suffix.
This class is found in java.util package. This class is declared with final. This class extends the Object class.
Stringjoiner Constructors:
1. Public StringJoiner (Char_Sequence delimiter)
This is an in-built parameterized constructor in the class StringJoiner. This takes in the delimiter, an constructs a StringJoiner having 0 characters in it. This StringJoiner neither has prefix nor suffix. So, if the provided delimiter is null, a NullPointerException is thrown.
2. Public StringJoiner (Char_Sequence delimiter, Char_Sequence prefix, Char_Sequence suffix)
Another parameterized constructor in the StringJoiner class. This class takes in three parameters which constitutes the delimiter and a prefix followed by suffix.
So, as the prefix and suffix parameters are provided, this will generate a StringJoiner having the copies of the supplied prefix, delimiter and suffix with 0 characters in it. If any one of the provided parameters, delimiter, prefix, suffix is null, a NullPointerException is thrown.
These are the in-built constructors in the StringJoiner Class. We can add our own constructors to this also, by extending StringJoiner class.
StringJoiner Methods:
There are many methods that are to be utilized for direct implementation. Some of the methods are:
1. add Method
The prototype for this method goes with
Public StringJoiner add (Char_Sequence newElement)
This method adds the copy of the provided newElement or Char_Sequence value to the StringJoiner value. This new element value can be null also. If the value is null, then null is added to the StringJoiner.
2. merge Method
The prototype for this method goes with
Public StringJoiner merge (StringJoiner other)
This method takes in a StringJoiner and adds the given StringJoiner contents as the next element without any prefix or suffix. If the given StringJoiner is empty or null, there will be no effect of performing the merge function.
3. Length Method
The prototype for this method goes with
Public int length ()
This method doesn’t takes in any parameters but can determine the length of the StringJoiner and returns the length of the StringJoiner of Integer type.
4. setEmptyValue Method
The prototype for this method goes with
Public StringJoiner setEmptyValue (Char_Sequence empty Value)
This method is generally used when we are determining the string representation of the StringJoiner with no elements are added yet.
5. toString Method
The prototype for this method goes with
Public String toString ()
For converting the StringJoiner to String, we will implement the toString method. So, this method returns the String value. This method will return all the prefix, suffix and the values added so far into the StringJoiner. So, if no values are added to the this method will return the prefix and suffix only.
Let’s look into the implementation of the StringJoiner in java
import java. io. * ;
import java. util. StringJoiner;
//Importing the package having StringJoiner.
public class StringJoinerDemo
{
public static void main (String [] args)
{
StringJoiner JoiningNames = new StringJoiner (",");
//Creating an object for StringJoiner Class.
JoiningNames. add ("Mahesh");
JoiningNames. add ("Kalavathi");
JoiningNames. add ("Peter");
JoiningNames. add (“Ayaan”);
JoiningNames. add (“Arha”);
//Add values using add method.
System.out.println (JoiningNames);
}
}
OUTPUT:
C: \Java> Mahesh, Kalavathi, Peter, Ayaan, Arha
So, in the above program the names are added to the StringJoiner object one by one. And if the object is printed, all the names are given separating every name with “,”.
StringJoiner Example for a StringJoiner with added prefix and suffix
import java.io.*;
import java. util. StringJoiner;
//Importing the package having StringJoiner.
public class StringJoinerDemo
{
public static void main (String [] args)
{
StringJoiner JoiningNames = new StringJoiner (",", “(“, “)”);
//Creating an object for StringJoiner Class.
JoiningNames. add ("Mahesh");
JoiningNames. add ("Kalavathi");
JoiningNames. add ("Peter");
JoiningNames. add (“Ayaan”);
JoiningNames. add (“Arha”);
//Add values using add method.
System.out.println (JoiningNames);
}
}
OUTPUT:
C: \Java>(Mahesh, Kalavathi, Peter, Ayaan, Arha)
The above code snippet has a call to the parameterized constructor in the StringJoiner class. This constructor takes in the delimiter, prefix and the suffix values.
Let’s understand the toString () Method by implementing in a java program.
import java. io. * ;
import java. util. StringJoiner;
//Importing the package having StringJoiner.
public class StringJoinerDemo
{
public static void main (String [] args)
{
StringJoiner strr = new StringJoiner (“ “);
//Creating an object for StringJoiner Class.
strr. add(“Programming”);
strr. add(“is”);
strr. add(“Human”);
strr. add(“Interaction”);
strr. add(“with”);
strr. add(“Computer.”);
//Add the values to the StringJoiner using the add method.
System.out.println (“StringJoiner: “, strr.toString ());
//Converting the StringJoiner to String using toString.
}
}
OUTPUT:
C: \Java> java StringJoinerDemo
Programming is Human Interaction with Computer.
In the above code snippet, all the values are added into the StringJoiner by using the add Method. At last, the StringJoiner is converted into the string by using the toString Method.
StringJoiner Example for merging two StringJoiner.
import java.io.*;
import java.util.StringJoiner;
public class StringJoinerDemo
{
Public static void main(String args[])
{
StringJoiner JoiningNames = new StringJoiner(“;”, “{“, “}”);
JoiningNames.add(“Krish”);
JoiningNames.add(“Peter”);
//Creating a StringJoiner with two names.
StringJoiner JoiningNames2 = new StringJoiner(“,”, “{“, “}”);
JoiningNames2.add(“Steven”);
JoiningNames2.add(“Stella”);
//Creating another StringJoiner with another two names.
StringJoiner mergeobj = JoiningNames.merge (JoiningNames2);
//Merging two StringJoiner into one.
System.out.println (mergeobj);
//Printing the merged object.
} //main
} //StringJoinerDemo
OUTPUT:
C: \Java>java StringJoinerDemo
[Krish; Peter; Steven, Stella]In the above code snippet, we created two StringJoiner and using another StringJoiner, these two StringJoiner are merged into one.
This is how merge Method in the StringJoiner class works.
StringJoiner class Methods Example
import java.io.*;
import java.util.StringJoiner;
public class StringJoinerDemo
{
public static void main (String [] args)
{
StringJoiner joiningNames = new StringJoiner (",");
// passing comma (,) as delimiter
// Prints nothing as it is empty
System.out.println (joiningNames);
// setting a default empty value using the Method setEmptyValue.
joiningNames.setEmptyValue ("StringJoiner is empty");
System.out.println (joiningNames);
// Adding values to StringJoiner one by one.
joiningNames.add ("Rohan");
joiningNames.add ("Ramya");
System.out.println (joiningNames);
// Returns length of StringJoiner using the length method of the StringJoiner class.
int length = joiningNames.length ();
System.out.println ("Length: "+length);
// Returns StringJoiner as String type
String strr = joiningNames.toString ();
System.out.println (strr);
// Now, we can apply String methods on it
char chr = str. charAt (2);
System. out. println ("Character at index 2: "+chr);
// Adding another more element
joiningNames. add ("Sirish");
System. out. println (joiningNames);
// Returns length
int new_Length = joiningNames. length ();
System. out. println ("New Length: "+new_Length);
} //main
} // StringJoinerDemo
OUTPUT:
C:/java> java StringJoinerDemo
StringJoiner is empty
Rohan, Ramya
Length: 11
Rohan, Ramya
Character at index 2: h
Rohan,Ramya,Sirish
New Length: 18