Question

我最近正在查看一个计算器，由于我的计算器，该网站上的用户向我建议，坦率地说，吸吮。这是计算器的代码：

import java.util.Scanner;

class RealCalc {

// Declare the constants
private static final String YES = "YES";

private static final String MULTIPLY = "Multiply";
private static final String DIVIDE = "Divide";
private static final String SUBTRACT = "Subtract";
private static final String ADD = "Add";

public static void main(String args[]) {

    // Using one only Scanner
    Scanner sc = new Scanner(System.in);
    double fnum, snum;

    System.out.println("Hello, my name is Cortana,"
            + " would you like to perform operations with me?");

    // Use equalsIgnoreCase to make it case-insensitive
    if(sc.nextLine().equalsIgnoreCase(YES)) {

        System.out.println("Good choice!\n");

        System.out.print("Enter your first number: ");
        fnum = sc.nextDouble();
        System.out.print("Enter your second number: ");
        snum = sc.nextDouble();

        // This is used to clear the '\n' character following the previous
        // integer input
        sc.nextLine();

        // Call the function to perform arithmetic operations
        performOperation(sc, fnum, snum);
    }

    System.out.println("Thank you!");
}

public static void performOperation(Scanner sc, double fnum, double snum) {

    System.out.println("\n" + MULTIPLY + ", " + DIVIDE + ", " + SUBTRACT + ", or " + ADD);
    System.out.println("What do you want me to do with these numbers?");    
    String operation = sc.nextLine();

    System.out.println();
    if(operation.equalsIgnoreCase(MULTIPLY)) {
        System.out.printf("%8.3f * %8.3f = %8.3f%n%n", fnum, snum, fnum * snum);
    }
    else if(operation.equalsIgnoreCase(DIVIDE)) {
        System.out.printf("%8.3f / %8.3f = %8.3f%n%n", fnum, snum, fnum / snum);
    }
    else if(operation.equalsIgnoreCase(SUBTRACT)) {
        System.out.printf("%8.3f - %8.3f = %8.3f%n%n", fnum, snum, fnum - snum);
    }
    else if(operation.equalsIgnoreCase(ADD)) {
        System.out.printf("%8.3f + %8.3f = %8.3f%n%n", fnum, snum, fnum + snum);
    }
    else {
        System.out.println("Sorry, I do not recognize this operation.\n");

        // Call this function again to re-prompt the user for a valid operation
        performOperation(sc, fnum, snum);
    }
}

}

我遇到的问题是输出。每当用户输入两个数字时，它将它们保存为两个不同的变量，fNum和sNum。所以我在想，为什么你不能放

System.out.println("Your answer is: " + (fNum * sNUM));
//Assuming it is multiplication

那么所有这些％的迹象和8.3f在哪里进来？任何帮助将不胜感激，谢谢

Answer 1

%是格式化打印（printf()）中使用的符号，作为将替换为值的占位符。常见示例包括浮点数%f，十进制整数%d和字符串%s。例如：

String greet = "Hello"
System.out.printf("%s world!", greet); //prints "Hello world!"

%8.3f表示浮点值的占位符，最小宽度为8，小数点后3位。如果该值包含少于8个字符，则默认情况下将在开头添加空格以填补空白。

虽然你可以使用你在答案中提到的连接，printf()更强大，更简洁，所以它更适合复杂的字符串格式化。

有关详细信息，请参阅this参考页。

Answer 2

简短的回答是肯定的，你可以简单地使用

System.out.println("Your answer is: " + (fNum * sNUM));

然而，这将显示您答案的所有小数位。％8.3f字符串告诉字符串格式化程序将浮点数编号为宽度为8个字符，小数点后面有3个字符，请查看java文档here

％符号在java

2 个答案: