java简单工厂模式实例及讲解

abstract class Operator {
 
    private double number1;
    private double number2;
    
       //用于四则运算类进行实现
    public abstract double getResult();
    
    public double getNumber1() {
        return number1;
    }
    public void setNumber1(double number1) {
        this.number1 = number1;
    }
    public double getNumber2() {
        return number2;
    }
    public void setNumber2(double number2) {
        this.number2 = number2;
    }
    
}

/**
 * 加法运算
**/
public class OperatorAdd extends Operator {
 
    @Override
    public double getResult() {
        return getNumber1() + getNumber2();
    }
 
}
 
/**
 * 减法运算
**/
 
public class OperatorSub extends Operator {
 
    @Override
    public double getResult() {
        return getNumber1() - getNumber2();
    }
}
 
/**
 * 乘法运算
**/
public class OperatorMul extends Operator {
 
    @Override
    public double getResult() {
        return getNumber1()*getNumber2();
    }
}
 
/**
 * 除法运算
**/
public class OperatorDiv extends Operator {
 
    @Override
    public double getResult() {
        if(getNumber2()==0) {
            try {
                throw new Exception("除数不能为0");
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return getNumber1()/getNumber2();
    }
}

public class OperatorFactory {
    
    public Operator createOperator(String op) {
        Operator operator = null;
        switch(op) {
            case "+" : operator = new OperatorAdd();break; 
            case "-" : operator = new OperatorSub();break;
            case "*" : operator = new OperatorMul();break;
            case "/" : operator = new OperatorDiv();break;
        }
        return operator;
    }
}

import org.junit.Test;
 
public class TestMain {
    @Test
    public void test() {
        OperatorFactory factory = new OperatorFactory();
        Operator operator = factory.createOperator("*");
        operator.setNumber1(10.2);
        operator.setNumber2(5.2);
        double result = operator.getResult();
        System.out.println(result);
    }
}