Question

我相当擅长Java和OOP，因此即使API是彻底的，Java中的许多概念也没有完全合理。我已经制作了一个小的计算器代码，但是我想学习如何使用方法中的参数来实现相同的产品，样本将是素数。

import java.io.IOException;
import java.util.Scanner;

public class Ga {

static Scanner input = new Scanner(System.in);
public static void main(String[] args) throws IOException {

    System.out.println("First number:");        
    float i = input.nextInt();

    System.out.println("Choose operator +, -, *, /");
    char s = input.next().charAt(0);

    System.out.println("Second number:");
    float z = input.nextInt();

    switch (s) {
        case '+':
            System.out.println("Result= "+(i+z));
            System.in.read();
            break;
        case '-':
            System.out.println("Result= "+(i-z));
            System.in.read();
            break;
        case '*':
            System.out.println("Result= "+(i*z));
            System.in.read();
            break;
        case '/':
            System.out.print("Result= "+(i/z));
            System.in.read();
            break;
    }

}
}

Answer 1

要从OOP开始，您可以编写一个表示操作的抽象类：

public abstract class Operation {
    public abstract float getResult(float a, float b);
}

然后，尝试编写像Addition，Division：

这样的具体操作

public class Addition extends Operation {
    @Override
    public float getResult(float a, float b) {
        return a + b;
    }
}
public class Division extends Operation {
    @Override
    public float getResult(float a, float b) {
        return a / b;
    }
}

然后，重写你的主要方法：

public static void main(String[] args) throws IOException {

    System.out.println("First number:");
    float i = input.nextInt();

    System.out.println("Choose operator +, -, *, /");
    char s = input.next().charAt(0);

    System.out.println("Second number:");
    float z = input.nextInt();

    Operation op = null;
    switch (s) {
    case '+':
        op = new Addition();
        break;
    case '-':
        op = new Subtraction();
        break;
            ...
    }

    System.out.println("Result= " + op.getResult(i, z));
    System.in.read();
}

正如理查德提到的那样，你也可以用HashMap重写开关：

public static void main(String[] args) throws IOException {

    System.out.println("First number:");
    float i = input.nextInt();

    System.out.println("Choose operator +, -, *, /");
    char s = input.next().charAt(0);

    System.out.println("Second number:");
    float z = input.nextInt();


    Map<String, Operation> operationMap = new HashMap<String, Operation>();
    operationMap.put("+", new Addition());
    operationMap.put("-", new Substraction());
    ...

    Operation op = operationMap.get(s);

    System.out.println("Result= " + op.getResult(i, z));
    System.in.read();

}

Answer 2

这是你在找什么？ https://stackoverflow.com/a/890980/3465623

如何在java中的方法中有效地使用参数？

2 个答案: