Class variables and methods in a singleton pattern implementation

Question

If we have a singleton class, say:

private static Singleton instance = new Singleton();

private Singleton() {

}

public static Singleton getInstance() {
    return instance;
}

Now we want to do the classic work. Add some global variables and methods, to simplify just think about getters. Imagine we need to global variables, say str1 and str2:

This two variables and their getters must be static or the fact that we are forcing this class to be a singleton is enough to ensure that only one instance of the class wil exists?

To be more precise:

   private String str1;
   private String str2;

          VS

   private static String str1;
   orivate static String str2;

           AND

   public String getStr1();
   public String getStr2();

          VS

   public static String getStr1();
   public static String getStr2();

James Wierzba · Accepted Answer · 2015-10-14 18:48:16Z

1

The private constructor will enforce having only one instance at a time. You should still follow standard OOP principles .

private static Singleton instance = new Singleton();

    private Singleton() {

    }

    public static Singleton getInstance() {
        return instance;
    }

    private String str1;
    private String str2;

    public String getStr1() { return str1; }
    public String getStr2() { return str2; }

}

edited Oct 14, 2015 at 18:48

answered Oct 14, 2015 at 18:45

James Wierzba

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2 Comments

Silva_PT_SCP Over a year ago

Inside the private constructor we can initialize the variables normally, right? One more question, for you the the "standard oop principle" is to use the static in a getter method?

James Wierzba Over a year ago

Ya, you initialize them just like you would normally. That static was a typo when I copy pasted from your question text !

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