Guava - Useful Classes

Guava - Collection Utilities

Guava - String Utilities

Guava - Primitive Utilities

Guava - Math Utilities

Guava - Useful Resources

Guava - Joiner Class

Quiz

Joiner provides various methods to handle joining operations on string, objects, etc.

Class Declaration

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

@GwtCompatible
public class Joiner
   extends Object

Sr.No	Method & Description
1	<A extends Appendable> A appendTo(A appendable, Iterable<?> parts) Appends the string representation of each of the parts, using the previously configured separator between each, to appendable.
2	<A extends Appendable> A appendTo(A appendable, Iterator<?> parts) Appends the string representation of each of the parts, using the previously configured separator between each, to appendable.
3	<A extends Appendable> A appendTo(A appendable, Object[] parts) Appends the string representation of each of the parts, using the previously configured separator between each, to appendable.
4	<A extends Appendable> A appendTo(A appendable, Object first, Object second, Object... rest) Appends to appendable the string representation of each of the remaining arguments.
5	StringBuilder appendTo(StringBuilder builder, Iterable<?> parts) Appends the string representation of each of the parts, using the previously configured separator between each, to builder.
6	StringBuilder appendTo(StringBuilder builder, Iterator<?> parts) Appends the string representation of each of the parts, using the previously configured separator between each, to builder.
7	StringBuilder appendTo(StringBuilder builder, Object[] parts) Appends the string representation of each of the parts, using the previously configured separator between each, to builder.
8	StringBuilder appendTo(StringBuilder builder, Object first, Object second, Object... rest) Appends to builder the string representation of each of the remaining arguments.
9	String join(Iterable<?> parts) Returns a string containing the string representation of the each of parts, using the previously configured separator between each.
10	String join(Iterator<?> parts) Returns a string containing the string representation of the each of parts, using the previously configured separator between each.
11	String join(Object[] parts) Returns a string containing the string representation of each of the parts, using the previously configured separator between each.
12	String join(Object first, Object second, Object... rest) Returns a string containing the string representation of each argument, using the previously configured separator between each.
13	static Joiner on(char separator) Returns a joiner which automatically places separator between consecutive elements.
14	static Joiner on(String separator) Returns a joiner which automatically places separator between consecutive elements.
15	Joiner skipNulls() Returns a joiner with the same behavior as this joiner, except automatically skipping over any provided null elements.
16	Joiner useForNull(String nullText) Returns a joiner with the same behavior as this one, except automatically substituting nullText for any provided null elements.
17	Joiner.MapJoiner withKeyValueSeparator(String keyValueSeparator) Returns a MapJoiner using the given key-value separator, and the same configuration as this Joiner otherwise.

Methods Inherited

This class inherits methods from the following class −

java.lang.Object

Example - Join Values while Skipping Null Values

GuavaTester.java

package com.tutorialspoint;

import java.util.Arrays;
import com.google.common.base.Joiner;

public class GuavaTester {
   public static void main(String args[]) {
      GuavaTester tester = new GuavaTester();
      tester.testJoiner();	
   }

   private void testJoiner() {
      System.out.println(Joiner.on(",")
         .skipNulls()
         .join(Arrays.asList(1,2,3,4,5,null,6)));
   }
}

Output

Run the GuavaTester and verify the output.

1,2,3,4,5,6

Example - Join Values while Replacing Null Values

GuavaTester.java

package com.tutorialspoint;

import java.util.Arrays;
import com.google.common.base.Joiner;

public class GuavaTester {
   public static void main(String args[]) {
      GuavaTester tester = new GuavaTester();
      tester.testJoiner();	
   }

   private void testJoiner() {
      System.out.println(Joiner.on(",")
         .useForNull("NONE")
         .join(Arrays.asList(1,2,3,4,5,null,6)));
   }
}

Output

Run the GuavaTester and verify the output.

1,2,3,4,5,NONE,6

Example - Join Objects

GuavaTester.java

package com.tutorialspoint;

import java.util.Arrays;
import com.google.common.base.Joiner;

public class GuavaTester {
   public static void main(String args[]) {
      GuavaTester tester = new GuavaTester();
      tester.testJoiner();	
   }

   private void testJoiner() {
      System.out.println(Joiner.on(",")
         .join(Arrays.asList(new Student(1, "Mahesh"), new Student(2,"Ramesh"))));
   }
}

class Student {
   private int rollNo;
   private String name;
   
   public Student(int rollNo, String name){
      this.rollNo = rollNo;
	  this.name = name;
   }
   
   public String toString(){
      return "[ Roll No:" + rollNo + ", Name: " + name +"]";    
   }
}

Output

Run the GuavaTester and verify the output.

[ Roll No:1, Name: Mahesh],[ Roll No:2, Name: Ramesh]

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