BE THE CODER > Java > Collections

The following example shows how to create an empty collection. Using empty collections instead of assigning null avoids NullPointerException. The Collections class provides several type safe methods which return empty collections which are both immutable and Serializable.

File Name :	com/bethecoder/tutorials/utils/collections/EmptyCollection.java
Author :	Sudhakar KV
Email :	[email protected]


package com.bethecoder.tutorials.utils.collections;



import java.util.Collection;

import java.util.Collections;

import java.util.List;

import java.util.Map;

import java.util.Set;



public class EmptyCollection {



  /**

   * @param args

   */

  public static void main(String[] args) {



    //Empty list of Strings

    List<String> strList = Collections.<String>emptyList();

    print(strList);

    

    //Empty list of Booleans

    List<Boolean> boolList = Collections.<Boolean>emptyList();

    print(boolList);

    

    //Empty list of Employees

    List<Emplooyee> empList = Collections.<Emplooyee>emptyList();

    print(empList);

    

    //Empty Set of Employees

    Set<Emplooyee> empSet = Collections.<Emplooyee>emptySet();

    print(empSet);

    

    //Empty Map of Employees

    Map<String, Emplooyee> empMap = Collections.<String, Emplooyee>emptyMap();

    System.out.println(empMap + " size : " + empMap.size());

  }



  public static void print(Collection<?> collection) {

    System.out.println(collection + " size : " + collection.size());

  }

}



class Emplooyee {

  private String name;



  public String getName() {

    return name;

  }



  public void setName(String name) {

    this.name = name;

  }

}

Empty Collection