java: 如何使用 printf 打印美元符号和带有 2 位小数的 double ？

Question

我对 printf 真的很不好。如何将 %$.2f 添加到我的字符串格式中，以便我可以获得如下所示的干净内容:(我之前忘记添加“$”)

MP3 Player cost:                        $580.39
Smart Phone cost:                       $510.93
Digital Watch cost:                     $495.99
Tablet cost:                            $643.17
Portable Gaming System cost:            $485.17



import java.util.Scanner;

public class test2 {

    public static void main(String[] arg) {

        Scanner in = new Scanner(System.in);

        int [][] matrix = { // 5 rows, 7 cols
                { 9, 13, 4, 7, 1, 14, 10},
                { 8, 2, 12, 11, 6, 15, 2},
                { 9, 6, 7, 10, 15, 8, 3},
                { 12, 14, 8, 15 ,2 , 7, 8},
                { 12, 10, 3, 11, 8, 3, 5},
        };

        String [] product = new String [5];
        product [0] = "MP3 Player";
        product [1] = "Smart Phone";
        product [2] = "Digital Watch";
        product [3] = "Tablet";
        product [4] ="Portable Gaming System";

        double [] price = {10.75, 15.27, 5.98, 9.67, 4.32, 12.50, 1.42}; // 7 elements

        costOfEach(matrix, product, price);
    }

    // compute and display the cost of manufacturing each device
    public static double costOfEach(int matrix[][], String[] product, double price [] ){
        double cost = 0.00;
        String item = "";
        double maxCost = 0.00;
        double minCost = Double.MAX_VALUE;
        int maxCostIndex = 0;
        int minCostIndex = 0;

就在这里。我尝试了很多组合但没有结果

        String format = "%-40s%s%n"; 
        for (int row = 0; row < matrix.length; row++){
             cost = 0;
             for (int col = 0, i = 0; col < matrix[0].length && i < price.length; col++, i++){

                 cost += matrix[row][col] * price [i]; 
             }

             System.out.printf(format, product[row] + " cost: $%.2f", cost);
        }
                return cost;
    }

}

Answer 1

上面的答案是正确的，要添加 $ 符号只需编辑以下行:

String format = "%-40s$%.2f%n";

你的输出:

MP3 Player cost:                        $580,39
Smart Phone cost:                       $510,93
Digital Watch cost:                     $495,99
Tablet cost:                            $643,17
Portable Gaming System cost:            $485,17