JAVA EXAMPLE PROGRAMS

Java Singleton Class Example Using Private Constructor

We can make constructor as private. So that We can not create an object outside of the class.
This property is useful to create singleton class in java.
Singleton pattern helps us to keep only one instance of a class at any time.
The purpose of singleton is to control object creation by keeping private constructor.

Java Singleton Sample Code

Code:

package com.myjava.constructors;

public class MySingleTon {
    
    private static MySingleTon myObj;
    /**
     * Create private constructor
     */
    private MySingleTon(){
        
    }
    /**
     * Create a static method to get instance.
     */
    public static MySingleTon getInstance(){
        if(myObj == null){
            myObj = new MySingleTon();
        }
        return myObj;
    }
    
    public void getSomeThing(){
        // do something here
        System.out.println("I am here....");
    }
    
    public static void main(String a[]){
        MySingleTon st = MySingleTon.getInstance();
        st.getSomeThing();
    }
}

Other Constructor Examples

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Interface and its usage

Interface is similar to a class which may contain method's signature only but not bodies and it is a formal set of method and constant declarations that must be defined by the class that implements it. Interfaces are useful for declaring methods that one or more classes are expected to implement, capturing similarities between unrelated classes without forcing a class relationship and determining an object's programming interface without revealing the actual body of the class.

Famous Quotations

The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.

-- William Arthur Ward

About Author

I'm Nataraja Gootooru, programmer by profession and passionate about technologies. All examples given here are as simple as possible to help beginners. The source code is compiled and tested in my dev environment.

If you come across any mistakes or bugs, please email me to [email protected].

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Reference: Java™ Platform Standard Ed. 7 - API Specification | Java™ Platform Standard Ed. 8 - API Specification | Java is registered trademark of Oracle.