java constructor privatization

The package constructor privatizes monomorphic mode;
 class preson{
     private  static preson newperson = new preson();
     private String name = "" ;
     private preson() { // package constructor 
        this .name = "Wang Wu" ;
    }
    public static preson getPreson() {
        return newperson;
    }
    public String getName() {
        return this.name;
    }
    public void setName(String n) {
        this.name = n;
    }
}
public  class monomorphic pattern {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        preson r1 = preson.getPreson();
        preson r2 = preson.getPreson ();
        preson r3 = preson.getPreson ();
        r2.setName( "Zhang San" );
        System.out.println(r3.getName()); // Output Zhang San 
    }

}

The monomorphic design pattern should be used where one class does not want to produce multiple objects.

Multiple stack memories point to the same heap memory.