java - 为什么这是一个错误？

Question

我在这一行收到错误“System.out.println((num1/dem1)(num2/dem2));”

错误提示:

该行有多个标记 - 赋值的左边必须是变量 - 标记“)”上的语法错误，AssignmentOperator 预计在之后 这个 token

package project;
import java.util.Scanner;

 public class summerproject {
 public static void main(String[] args)  
    {
     Scanner in = new Scanner( System.in );
     {
    //INPUT NUMBERS
     System.out.println("Enter Numerator 1. ");
     int num1 = in.nextInt(); 
     System.out.println("Enter Denominator 1. ");
     int dem1 = in.nextInt();
     System.out.println("Enter Numerator 2. ");
     int num2 = in.nextInt();
     System.out.println("Enter Denominator 2. ");
     int den2 = in.nextInt();
     }
     System.out.println("Press 1 to multiply");
     int mult = in.nextInt();


     if (mult == 1)
     {
         System.out.println((num1/dem1)(num2/dem2));   
     }
    }//ARGS BRACKET      
 }//END BRACKET

Answer 1

该行无效:

System.out.println((num1/dem1)(num2/dem2));

(num1/dem1) 和 (num2/dem2) 之间需要有一个运算符。例如，要将两个表达式相乘，请使用 * 运算符:

(num1/dem1)*(num2/dem2)

Java 的行为不太像数学，在数学中，串联意味着乘法。相反，您必须显式地将操作数相乘。

<小时/>

此外，您声明

int den2 = in.nextInt();

这应该是

int dem2 = in.nextInt().

<小时/>

适当调整大括号并进行上述修复后，您最终应该得到:

public class summerproject {

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

        //INPUT NUMBERS
        System.out.println("Enter Numerator 1. ");
        int num1 = in.nextInt();
        System.out.println("Enter Denominator 1. ");
        int dem1 = in.nextInt();
        System.out.println("Enter Numerator 2. ");
        int num2 = in.nextInt();
        System.out.println("Enter Denominator 2. ");
        int dem2 = in.nextInt();

        System.out.println("Press 1 to multiply");
        int mult = in.nextInt();

        if (mult == 1) {
            System.out.println((num1 / dem1) * (num2 / dem2));
        }
    }
}

<小时/>

运行示例:

Enter Numerator 1. 
20
Enter Denominator 1. 
4
Enter Numerator 2. 
30
Enter Denominator 2. 
5
Press 1 to multiply
1
30