java我怎样才能让它执行到小数点后两位，作为长小数点

Question

int ptstotal, ptsearned, ptssofar;
ptstotal= 1500;
ptsearned= 750;
ptssofar= 950;

System.out.println("The current percentage is "+(int)Math.round(ptsearned*1)/(double)(ptssofar)*100+"%.");

System.out.println("The current percentage is "+Math.round(ptsearned*1)/(double)ptssofar*100+"%.");

输出为长十进制78.96736805263%，只需要78.97%需要帮助

Answer 1

把一个数字乘以1，或者对一个你知道是整数的量调用Math.round是没有意义的。保持简单

double percentage = (double)ptsearned / ptssofar * 100;
System.out.format("The current percentage is %.2f%%%n", percentage);

在这里，需要(double)来避免整数除法。然后，在格式字符串中，%.2f表示用两位小数显示该值。下一个%%被转换为百分号，最后一个%n被转换为行分隔符

Answer 2

试着改用printf

double value = (int)Math.round(ptsearned*1)/(double)(ptssofar)*100;
System.out.printf("The current percentage is %.2f %",value);

Answer 3

你可以用^{}或formatted output和^{}一样

DecimalFormat df = new DecimalFormat("###.00");
System.out.println("The current percentage is "
        + df.format(Math.round(ptsearned * 1) / (double) (ptssofar)
                * 100) + "%.");
System.out.printf("The current percentage is %.2f%%.%n",
        Math.round(ptsearned * 1) / (double) ptssofar * 100);

哪些输出（请求的）

The current percentage is 78.95%.
The current percentage is 78.95%.