5 design patterns every Android developer should know - Singleton pattern

Singleton.java

public class Singleton {
    //instance holder
    private static Singleton mInstance = null;

    private String mString;
    
    //prevent others from instantiating the class with new keyword
    private Singleton(){
        mString = "Hello";
    }
    
    //public method to get the Singelton instance
    public static Singleton getInstance(){
        //check if it wasn't created before
        if(mInstance == null) {
            mInstance = new Singleton();
        }
        return mInstance;
    }

    public String getString(){
        return this.mString;
    }

    public void setString(String value){
        mString = value;
    }
}