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Singleton<br />
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When there is only one instance creation is allowed<br />
OR<br />
We want to restrict instance creation of particular class and allow only one instance.<br />
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In such scenarios, we use Singleton Design Pattern. I have explained Singleton design pattern in detail in video below:-<br />
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Source Code is given below:-<br />
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<pre class="prettyprint" style="overflow: scroll; text-align: left;"><code class="language-java">
package com.techiekunal.codepractice.designpatterns;

/**
 * Basic Singleton Example with Eager initialization
 * 
 * @author kunalsaxena
 *
 */
public class SingletonEagerExample {

 private static final SingletonEagerExample INSTANCE = new SingletonEagerExample();
 
 // prevent instamce creation from outside
 private SingletonEagerExample() {
  
 }
 
 /**
  * public method to get instance
  * static so that it can be accessed without object.
  * outside world will not be able to create object
  * 
  * @return
  */
 public static SingletonEagerExample getInstance() {
  return INSTANCE;
 }
 
}

</code>
</pre>
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When there is only one instance creation is allowed OR We want to restrict instance creation of particular class and allow only one instance.