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Most people do not understand the knowledge points of this article "how to write the code of Java factory design pattern", so the editor summarizes the following content, detailed content, clear steps, and has a certain reference value. I hope you can get something after reading this article. Let's take a look at this "how to write the code of Java factory design pattern" article.

Realization method

We will create a Shape interface and a concrete class that implements the Shape interface. A factory class ShapeFactory is defined in the next step.

FactoryPatternDemo this is a demo class that uses ShapeFactory to get a Shape object. It passes the information (CIRCLE/RECTANGLE/SQUARE) to ShapeFactory to get the desired object type.

The structure of implementing the factory pattern is shown in the following figure-

Java-61.jpg

Step 1

Create an interface-

Shape.java

PublicinterfaceShape {

Voiddraw ()

}

Step 2

Create a concrete class that implements the same interface. Several classes are shown below-

Rectangle.java

PublicclassRectangleimplementsShape {

@ Override

Publicvoiddraw () {

System.out.println ("InsideRectangle::draw () method.")

}

}

Square.java

PublicclassSquareimplementsShape {

@ Override

Publicvoiddraw () {

System.out.println ("InsideSquare::draw () method.")

}

}

Circle.java

PublicclassCircleimplementsShape {

@ Override

Publicvoiddraw () {

System.out.println ("InsideCircle::draw () method.")

}

}

Step 3

Create a factory to generate objects of a specific class based on the given information.

ShapeFactory.java

PublicclassShapeFactory {

/ / usegetShapemethodtogetobjectoftypeshape

PublicShapegetShape (StringshapeType) {

If (shapeType==null) {

Returnnull

}

If (shapeType.equalsIgnoreCase ("CIRCLE")) {

ReturnnewCircle ()

} elseif (shapeType.equalsIgnoreCase ("RECTANGLE")) {

ReturnnewRectangle ()

} elseif (shapeType.equalsIgnoreCase ("SQUARE")) {

ReturnnewSquare ()

}

Returnnull

}

}

Step 4

Use a factory to get objects of a specific class by passing information such as types.

FactoryPatternDemo.java

PublicclassFactoryPatternDemo {

Publicstaticvoidmain (String [] args) {

ShapeFactoryshapeFactory=newShapeFactory ()

/ / getanobjectofCircleandcallitsdrawmethod.

Shapeshape1=shapeFactory.getShape ("CIRCLE")

/ / calldrawmethodofCircle

Shape1.draw ()

/ / getanobjectofRectangleandcallitsdrawmethod.

Shapeshape2=shapeFactory.getShape ("RECTANGLE")

/ / calldrawmethodofRectangle

Shape2.draw ()

/ / getanobjectofSquareandcallitsdrawmethod.

Shapeshape3=shapeFactory.getShape ("SQUARE")

/ / calldrawmethodofcircle

Shape3.draw ()

}

}

Step 5

Verify that the output is as follows-

InsideCircle::draw () method.

InsideRectangle::draw () method.

InsideSquare::draw () method.

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