設計模式——簡單工廠模式

工做以後，一直忙於工做，像一位前輩所說的那樣，個人確須要好好總結一下所學所用過的知識了。

就從複習設計模式開始，今天覆習的是簡單工廠設計模式。

如設計一個簡單的計算器程序：

  須要從Console端得到兩個數字、一個運算符（＋－＊／），並計算得出結果。

  

此處可利用簡單工廠根據運算符生成運算類，類圖以下：

package sf.simpleFactory;

import sf.simpleFactory.Operator.DivisionOperator;
import sf.simpleFactory.Operator.MinusOperator;
import sf.simpleFactory.Operator.MultipleOperator;
import sf.simpleFactory.Operator.PlusOperator;

public class OperatorFactory {
    public static Operator getInstance(int digit1, int digit2, String operator) {
        if (operator.equals("+")) {
            return new PlusOperator(digit1, digit2, operator);
        } else if (operator.equals("-")) {
            return new MinusOperator(digit1, digit2, operator);
        } else if (operator.equals("*")) {
            return new MultipleOperator(digit1, digit2, operator);
        } else if (operator.equals("/")) {
            return new DivisionOperator(digit1, digit2, operator);
        } else {
            return null;
        }
    }
}

package sf.simpleFactory;

public abstract class Operator {
    public int digit1;
    public int digit2;
    public Operator(int digit1, int digit2, String operator) {
        this.digit1 = digit1;
        this.digit2 = digit2;
    }
    public abstract float calculate();

    public static class PlusOperator extends Operator{
        public PlusOperator(int digit1, int digit2, String operator) {
            super(digit1, digit2, operator);
        }
        @Override
        public float calculate() {
            return digit1 + digit2;
        }
    }
    
    public static class MinusOperator extends Operator{
        public MinusOperator(int digit1, int digit2, String operator) {
            super(digit1, digit2, operator);
        }
        @Override
        public float calculate() {
            return digit1 - digit2;
        }
    }
    
    public static class MultipleOperator extends Operator{
        public MultipleOperator(int digit1, int digit2, String operator) {
            super(digit1, digit2, operator);
        }
        @Override
        public float calculate() {
            return digit1 * digit2;
        }
    }
    
    public static class DivisionOperator extends Operator{
        public DivisionOperator(int digit1, int digit2, String operator) {
            super(digit1, digit2, operator);
        }
        @Override
        public float calculate() {
            return digit1 / digit2;
        }
    }
}