Joiner class | Guava | Java

Last Updated : 15 Nov, 2018

Guava’s Joiner class provides various methods to handle joining operations on string, objects, etc. This class provides advanced functionality for the join operation.

Declaration: Following is the declaration for com.google.common.base.Joiner class :

@GwtCompatible
public class Joiner
   extends Object

The following table gives a brief summary of the methods provided by Guava’s Joiner class:

Example:

// Java code to show implementation of 
// Guava's Joiner class's method 
  
import com.google.common.base.Joiner; 
import java.util.*; 
  
class GFG { 
  
    // Driver's code 
    public static void main(String[] args) 
    { 
  
        // Creating a string array 
        String[] arr = { "one", "two", "three", "four" }; 
        System.out.println("Original Array: "
                           + Arrays.toString(arr)); 
  
        // Use Joiner to combine all elements. 
        // ... Specify delimiter in on method. 
  
        // The last part of the Joiner statement, join, 
        // can receive an Iterable (like an ArrayList) or 
        // an Object array. It returns a String. 
        String result = Joiner.on("...") 
                            .join(arr); 
  
        System.out.println("Joined String: "
                           + result); 
    } 
} 

Output:

Original Array: [one, two, three, four]
Joined String: one...two...three...four

Some more methods provided by Guava’s Joiner class are:

Example:

// Java code to show implementation of 
// Guava's Joiner class's method 
  
import com.google.common.base.Joiner; 
import java.util.*; 
  
class GFG { 
  
    // Driver's code 
    public static void main(String[] args) 
    { 
  
        // Creating a string array 
        String[] arr = { "one", "two", null, 
                         "four", null, "five" }; 
        System.out.println("Original Array: "
                           + Arrays.toString(arr)); 
  
        // Unlike the standard join method, we can 
        // filter elements with a Joiner. With skipNulls, 
        // null elements in an array or Iterable are removed. 
        // Often null elements are not needed. 
        // $$ Specify delimiter in on method. 
  
        // The last part of the Joiner statement, join, 
        // can receive an Iterable (like an ArrayList) or 
        // an Object array. It returns a String. 
        String result = Joiner.on('+') 
                            .skipNulls() 
                            .join(arr); 
  
        System.out.println("Joined String: "
                           + result); 
    } 
} 

Output:

Original Array: [one, two, null, four, null, five]
Joined String: one+two+four+five

Reference: Google Guava Joiner Class

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