如何在另一个班级中调用班级

lets say I have a Main class which my main program runs with it.

假设我有一个Main类,我的主程序随之运行。

public calss Main{
   public static void main(String[] args){
       System.out.print("input Length ");
       a = in.nextInt();
       System.out.print("input Height ");
       b = in.nextInt();
       ...
       (The code that goes in between?)
       ...
       System.out.println("output");
   }
}

How can I use another class and input it in side my first class lets say if its a simple calculation class like

我如何使用另一个类并在第一个类的侧面输入它,让我们说它是一个简单的计算类

pubic class Math{
    output = a*b
}

and have like this input and output:

并喜欢这个输入和输出:

input Length 2
input Height 3
6

By the way don't vote down for me cause I'm noob! common why you do this? XD

顺便说一句,不要为我投票,因为我是菜鸟!你为什么这么做? XD

3 个解决方案

#1

Its simple as that.

它很简单。

public class Test{
  public int multiplication(int a, int b){
   return a*b;
  }

  public static void main(String[] args){
       System.out.print("input Length ");
       a = in.nextInt();
       System.out.print("input Height ");
       b = in.nextInt();
       ...
       Test t = new Test();
       System.out.println(t.multiplication(a,b));
   }
}

#2

You are confusing a class with a method there.

你在课堂上混淆了一个方法。

If you want to put your calculation method in a class

如果要将计算方法放在类中

e.g.

public class MyCalc {
    public static int calculate(int a, int b) { 
         return a*b;
    }
}

Then you could call that function from with your main

然后你可以用你的主要来调用那个功能

public static void main(String[] args) {

     // something


     int result = MyCalc.calculate(1,2);
}

That's how you'd use static functions in a utility class to modularise some functionality. Does that help?

这就是你如何在实用程序类中使用静态函数来模块化某些功能。这有帮助吗?

#3

Your second class may have fields and methods as well. For your example, your Math class should have a method were you perform the multiplication of two integers, and it should receive these integers as parameters. Here's a small example on it:

你的第二堂课也可能有田野和方法。对于您的示例,您的Math类应该有一个方法,如果您执行两个整数的乘法,它应该接收这些整数作为参数。这是一个小例子:

public class Math {
    //declaring the method as static
    //no need to create an instance of the class to use it
    //the method receives two integer arguments, a and b
    //the method returns the multiplication of these numbers
    public static int multiply(int a, int b) {
        return a * b;
    }
}

But be careful, do not name your class with the same name of built-in classes in Java, **specially classes in java.lang package. Yes, there is a built-in Math class in Java.

但是要小心,不要在Java中使用相同的内置类命名您的类,**特别是java.lang包中的类。是的,Java中有一个内置的Math类。

So, it would be better to rename your class to something like this:

因此,最好将您的类重命名为以下内容:

public class IntegerOperations {
    public static int multiply(int a, int b) {
        return a * b;
    }
}

And you will use it like this (after fixing your current code):

你会像这样使用它(修复你当前的代码后):

public class Main {
    public static void main(String[] args) {
        //Use a Scanner to read user input
        Scanner in = new Scanner(System.in);

        System.out.print("input Length ");
        //declare the variables properly
        int a = in.nextInt();
        System.out.print("input Height ");
        int b = in.nextInt();

        //declare another variable to store the result
        //returned from the method called
        int output = Operations.multiply(a, b);

        System.out.println("output: " + output);
    }
}

#1