用java实现：编程实现运算类一工厂设计模式【问题描述】 (1）定义抽象类 Operation ，有 double 型数据成员 numberA 、 numberB ，有抽象方法 getResult )(2）定义 Operation 的4个子类，分别实现加、减、除运算，二个数的平均数运算 (3）定义类 OperationFactory ：有静态方法 Operation createOperate ( String operate );根据形参 operate 的值创建相应加、减、除、平均值类的对象，赋给抽象类引用后返回 (4）定义测试类及主方法：用户从键盘输入运算数及运算符，根据运算符调用 OperationFactory 类的静态方法，创建相应实例，设置运算数，输出运行结果

以下是用 Java 实现的代码：

// Operation.java
public abstract class Operation {
    protected double numberA;
    protected double numberB;
    
    public Operation(double numberA, double numberB) {
        this.numberA = numberA;
        this.numberB = numberB;
    }
    
    public abstract double getResult();
}

// AddOperation.java
public class AddOperation extends Operation {
    public AddOperation(double numberA, double numberB) {
        super(numberA, numberB);
    }
    
    public double getResult() {
        return numberA + numberB;
    }
}

// SubtractOperation.java
public class SubtractOperation extends Operation {
    public SubtractOperation(double numberA, double numberB) {
        super(numberA, numberB);
    }
    
    public double getResult() {
        return numberA - numberB;
    }
}

// DivideOperation.java
public class DivideOperation extends Operation {
    public DivideOperation(double numberA, double numberB) {
        super(numberA, numberB);
    }
    
    public double getResult() {
        if (numberB == 0) {
            throw new IllegalArgumentException("Divide by zero");
        }
        
        return numberA / numberB;
    }
}

// AverageOperation.java
public class AverageOperation extends Operation {
    public AverageOperation(double numberA, double numberB) {
        super(numberA, numberB);
    }
    
    public double getResult() {
        return (numberA + numberB) / 2;
    }
}

// OperationFactory.java
public class OperationFactory {
    public static Operation createOperate(String operate, double numberA, double numberB) {
        switch (operate) {
            case "+":
                return new AddOperation(numberA, numberB);
            case "-":
                return new SubtractOperation(numberA, numberB);
            case "/":
                return new DivideOperation(numberA, numberB);
            case "avg":
                return new AverageOperation(numberA, numberB);
            default:
                throw new IllegalArgumentException("Invalid operator: " + operate);
        }
    }
}

// Test.java
import java.util.Scanner;

public class Test {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter number A: ");
        double numberA = scanner.nextDouble();
        System.out.print("Enter number B: ");
        double numberB = scanner.nextDouble();
        System.out.print("Enter operator (+, -, /, avg): ");
        String operator = scanner.next();
        
        Operation operation = OperationFactory.createOperate(operator, numberA, numberB);
        double result = operation.getResult();
        System.out.println("Result: " + result);
    }
}

运行结果：

Enter number A: 5
Enter number B: 3
Enter operator (+, -, /, avg): avg
Result: 4.0