如何在Java中正确使用printf格式化

Question

我正在尝试创建一个简单的程序来接收三个项目,它们的数量和价格,并将它们全部加在一起以创建一个简单的收据类型格式.我的教授给了我一个特定的收据格式,其中所有小数都排成一行并且一致地放置.它看起来应该是这样的.

Your Bill:


Item                           Quantity       Price         Total
Diet Soda                            10        1.25         12.50
Candy                                1         1.00          1.00
Cheese                               2         2.00          4.00


Subtotal                                                    17.50
6.25% Sales Tax                                              1.09
Total                                                       18.59

我的教授指出名称应该有30个字符,数量和价格应该是10个字符和总数.这样做我必须使用printf方法.到目前为止,我正在尝试使用此代码对其进行格式化.

import java.util.Scanner;
class AssignmentOneTest {

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

        // System.out.printf("$%4.2f for each %s ", price, item);
        // System.out.printf("\nThe total is: $%4.2f ", total);

        // process for item one
        System.out.println("Please enter in your first item");
        String item = kb.nextLine();
        System.out.println("Please enter the quantity for this item");
        int quantity = Integer.parseInt(kb.nextLine());
        System.out.println("Please enter in the price of your item");
        double price = Double.parseDouble(kb.nextLine());

        // process for item two
        System.out.println("Please enter in your second item");
        String item2 = kb.nextLine();
        System.out.println("Please enter the quantity for this item");
        int quantity2 = Integer.parseInt(kb.nextLine());
        System.out.print("Please enter in the price of your item");
        double price2 = Double.parseDouble(kb.nextLine());
        double total2 = quantity2 * price2;
        // System.out.printf("$%4.2f for each %s ", price2, item2);
        // System.out.printf("\nThe total is: $%4.2f ", total2);

        // process for item three
        System.out.println("Please enter in your third item");
        String item3 = kb.nextLine();
        System.out.println("Please enter the quantity for this item");
        int quantity3 = Integer.parseInt(kb.nextLine());
        System.out.println("Please enter in the price of your item");
        double price3 = Double.parseDouble(kb.nextLine());
        double total3 = quantity3 * price3;
        // System.out.printf("$%4.2f for each %s ", price3, item3);
        // System.out.printf("\nThe total is: $%4.2f ", total3);

        double total = quantity * price;

        double grandTotal = total + total2 + total3;
        double salesTax = grandTotal * (.0625);
        double grandTotalTaxed = grandTotal + salesTax;

        String amount = "Quantity";
        String amount1 = "Price";
        String amount2 = "Total";
        String taxSign = "%";

        System.out.printf("\nYour bill: ");
        System.out.printf("\n\nItem");
        System.out.printf("%30s", amount);
        // System.out.printf("\n%s %25d %16.2f %11.2f", item, quantity, price,
        // total);
        // System.out.printf("\n%s %25d %16.2f %11.2f", item2,quantity2, price2,
        // total2);
        // System.out.printf("\n%s %25d %16.2f %11.2f", item3,quantity3, price3,
        // total3);

        System.out.printf("\n%s", item);
        System.out.printf("%30d", quantity);
        System.out.printf("\n%s", item2);
        System.out.printf("\n%s", item3);

        System.out.printf("\n\n\nSubtotal %47.2f", grandTotal);
        System.out.printf("\n6.25 %s sales tax %39.2f", taxSign, salesTax);
        System.out.printf("\nTotal %50.2f", grandTotalTaxed);    
    }
}

如果我输入更长的商品名称,则会移动数量,价格和总数的位置.我的问题是,如何使用printf创建一个有限宽度的设置起点,请帮忙.

Answer 1

System.out.printf("%1$-30s %2$10d %3$10.2f %4$10.2f", "Diet Soda", 10, 1.25, 12.50);

将打印线

Diet Soda                              10       1.25      12.50

传递给该printf方法的第一个字符串是一系列格式说明符,用于描述我们希望如何打印其余参数.在格式说明符周围,您可以添加其他也将打印的字符(不进行格式化).

上面的格式说明符具有以下语法:
%[index$][flags][width][.precision]conversionwhere []表示可选.

% 开始格式化表达式.

[index$]表示要格式化的参数的索引.索引从1开始.上面的索引实际上并不需要,因为没有索引的每个格式说明符都被指定为从1开始计数.

[-] 上面使用的唯一标志,将输出对齐到左侧.

[width] 表示要打印的最小字符数.

[.precision] 在这种情况下,小数点后要写入的位数,尽管这会随着不同的转换而变化.

conversion指示如何格式化参数的字符.d是十进制整数,f是浮点的十进制格式,s在我们的例子中不改变字符串.

更多信息可以在这里找到.