Simple Engineering and single case

Simple engineering:

First create a class with a computer as an example

public class Operationfactory

{

Write a method that returns the required type of static to facilitate invocation of the class name point

Public static operation getinitstance(String calc)

{

Operation Ope =null;

Switch (Calc)

{

Case "+":

Ope =new Add ();

Berak

Case "-":

Ope =new Sub ();

Berak

Case "*":

Ope =new Mul ();

Berak

Case "/":

Ope =new Div ();

Berak

}

　　　　　return ope;

}

}

Single Example:

Public person ()

{

To define a static variable first

public static person per;

Define non-parametric constructs as private

Private person ()

{}

To define a static method

public static person Getinitance ()

{

if (per==null)

{

OPR =new person ();

}

return OPR;

}

}

Simple Engineering and single example