Question

我正在上普林斯顿大学的算法课程，并且第一个编程任务需要以这种方式输出结果：

mean                    = 0.5929934999999997
stddev                  = 0.00876990421552567
95% confidence interval = [0.5912745987737567, 0.5947124012262428]

我考虑过字符串格式化，因为在他们的头脑中没有人会计算缩进的空格：

    String confidence = "95% confidence interval";
    int width = confidence.length();
    String f = "%-".concat(String.valueOf(width)).concat("s = ");
    System.out.printf(f.concat("%f\n"), "mean", stats.mean());
    System.out.printf(f.concat("%f\n"), "stddev", stats.stddev());
    System.out.printf(f.concat("[%f, %f]"), confidence, stats.confidenceLo(), stats.confidenceHi());

但令我遗憾的是，程序将截断两次截断以使其浮动：

mean                    = 0.591316
stddev                  = 0.009776
95% confidence interval = [0.589400, 0.593232]

这么说，有没有办法格式化整个双精度数字？

Answer 1

在这种情况下使用DecimalFormat，例如：

    double mean = 0.592993499999999;
    NumberFormat formatter = new DecimalFormat("#0.000000000000000");
    System.out.println(formatter.format(mean));

Answer 2

使用16个小数位格式“％.16f”

String confidence = "95% confidence interval";
int width = confidence.length();
String f = "%-".concat(String.valueOf(width)).concat("s = ");
System.out.printf(f.concat("%.16f\n"), "mean", stats.mean());
System.out.printf(f.concat("%.16f\n"), "stddev", stats.stddev());
System.out.printf(f.concat("[%.16f, %.16f]"), confidence, stats.confidenceLo(), stats.confidenceHi());

Answer 3

我使用了String.valueOf(aDoubleNumber)方法并将printf语句中的％f更改为％s。这对我有用。

public static void main(String[] args)
    {
        double mean = 0.5929934999999997;
        double stddev = 0.00876990421552567;
        double confidenceLo = 0.12345666612123;
        double confidenceHi = 0.123456784435369;

        String confidence = "95% confidence interval";
        int width = confidence.length();
        String f = "%-".concat(String.valueOf(width))
            .concat("s = ");

        // changed the %f to %s and used String.valueOf method to convert first
        System.out.printf(f.concat("%s\n"), "mean", String.valueOf(mean));
        System.out.printf(f.concat("%s\n"), "stddev", String.valueOf(stddev));
        System.out.printf(f.concat("[%s, %s]"), confidence,
                (String.valueOf(confidenceLo)), String.valueOf(confidenceHi));
    }

输出：

平均值= 0.5929934999999997

stddev = 0.00876990421552567

95％置信区间= [0.12345666612123，0.123456784435369]

如何显示双精度而不截断字符串格式的浮点数？

3 个答案: