Google Guava Collections

• Google Guava API provides collections, caching, primitives support, concurrency libraries, common annotations, string processing.

• This library can be downloaded from :- 

          http://code.google.com/p/guava-libraries/

Project Structure:-

Test Data:-

• We will build some demo data to test the Google Guava API. We will take Student as Value object.

Student.java:-

package com.sandeep.google.guava;

import java.io.Serializable;

public class Student implements Serializable {

 private static final long serialVersionUID = 1L;

 private String name;

 private int roll;

 public String getName() {
  return name;
 }

 public void setName(String name) {
  this.name = name;
 }

 public int getRoll() {
  return roll;
 }

 public void setRoll(int roll) {
  this.roll = roll;
 }

 @Override
 public String toString() {
  return "Student [name=" + name + ", roll=" + roll + "]";
 }

}

StudentDemoDataService.java:-

package com.sandeep.google.guava;

import java.util.ArrayList;
import java.util.List;

public class StudentDemoDataService {

 public static List getListOfStudents() {

  List listOfStudent = new ArrayList();
  Student s1 = new Student();
  s1.setName("Sandeep");
  s1.setRoll(23);
  Student s2 = new Student();
  s2.setName("Surabhi");
  s2.setRoll(33);
  Student s3 = new Student();
  s3.setName("Sumanta");
  s3.setRoll(25);
  Student s4 = new Student();
  s4.setName("Sangeeta");
  s4.setRoll(23);
  Student s5 = null;
  listOfStudent.add(s1);
  listOfStudent.add(s2);
  listOfStudent.add(s5);
  listOfStudent.add(s3);
  listOfStudent.add(s4);

  return listOfStudent;

 }

}

Guava Joiner & Splitter:-

• This feature of Guava provides adding and splitting of toString() methods of objects.

• It provides a controlled accessibility to NULL value and objects.

Testing Joiner & Splitter:-

• Concatenating Objects toString with # and splitting the String to sub strings.

package com.sandeep.google.guava;

import java.util.Iterator;
import java.util.List;
import com.google.common.base.Joiner;
import com.google.common.base.Splitter;

public class GoogleGuavaCollectionDemo {

 public static void main(String[] args) {

  List listOfStudent = StudentDemoDataService
    .getListOfStudents();

  Joiner joiner = Joiner.on("#").skipNulls();
  String joinedString = joiner.join(listOfStudent);
  System.out.print("Joined String : " + joinedString + "n");

  Splitter splitter = Splitter.on("#");
  Iterable itrString = splitter.split(joinedString);
  Iterator itr = itrString.iterator();

  while (itr.hasNext()) {

   String elementString = itr.next();
   System.out.print("elementString : " + elementString + "n");
  }

 }

}

Output:-

Joined String : Student [name=Sandeep, roll=23]#Student [name=Surabhi, roll=33]#Student [name=Sumanta, roll=25]#Student [name=Sangeeta, roll=23]
elementString : Student [name=Sandeep, roll=23]
elementString : Student [name=Surabhi, roll=33]
elementString : Student [name=Sumanta, roll=25]
elementString : Student [name=Sangeeta, roll=23]

Guava Funnel and Filter:-

• Guava filters are based on Bloom Filter . This is based on a data Structure to rapidly and memory efficiently searched an element. It is based on bit vector.

package com.sandeep.google.guava;

import java.util.List;

import com.google.common.hash.BloomFilter;
import com.google.common.hash.Funnel;
import com.google.common.hash.PrimitiveSink;

public class GuavaFunnelDemo {

 @SuppressWarnings("serial")
 public static void main(String[] args) {

  // Creating a Student Funnel
  Funnel studentFunnel = new Funnel() {

   @Override
   public void funnel(Student aStudent, PrimitiveSink intoStudentFunnel) {

    intoStudentFunnel.putString(aStudent.getName()).putInt(
      aStudent.getRoll());
   }
  };

 // Student Filter for a funnel type Stusdent with expected insertion 10
  BloomFilter studentBloomFilter = BloomFilter.create(
    studentFunnel, 10, 0.01);
  List listOfStudent = StudentDemoDataService
    .getListOfStudents();
  for (Student aStudent : listOfStudent) {

   if (aStudent != null) {

    studentBloomFilter.put(aStudent);
   }

  }

  Student anotherStudent = new Student();
  anotherStudent.setName("Sandeep");
  anotherStudent.setRoll(23);
  boolean mightContain = studentBloomFilter.mightContain(anotherStudent);
  System.out.print("Might Contain : " + mightContain + "n");

 }
}

Output:-

Might Contain : true

Guava Optional:-

package com.sandeep.google.guava;

import com.google.common.base.Optional;

public class GuavaBasicUtilitiesDemo {

 public static void main(String[] args) {

  Student dummyStudent = new Student();
  dummyStudent.setName("Dummy Name");
  dummyStudent.setRoll(0);
  Optional opt = Optional.of(dummyStudent);
  System.out.println(opt.isPresent());

 }

}

output:-

true

Code Download:-

Guava code download