Rounding off a decimal to 2 places-CodePudding

Code

package Java.School.IX;
import java.util.*;

public class Invest {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter principle - Rs ");
        double p = sc.nextDouble();
        //Interest for 1st yr - 
        double i1 = (p*3*5)/100;
        double a = Math.round(i1,2);
        System.out.println("Interest for 1st year is Rs "   a);
        //Interest for 2nd yr - 
        double p1 = p   i1;
        double i2 = (p1*3*5)/100; 
        System.out.println("Interest for 2nd year is Rs "  i2); 
        sc.close();
    }
}

Issue

I tried using Math.round(double, noOfPlaces), but this code doesn't seem to be working. I need some guidance.

Pls help me to round of the decimal to 2 decimal places. How to fix this?

CodePudding user response：

There are multiple ways to do this.

Math.round()

double i = 2.3333;
System.out.println(Math.round(i*100) / 100);

NumberFormat.format()

NumberFormat formatter = new DecimalFormat("#0.00");     
System.out.println(formatter.format(2.3333));

System.out.printf()

System.out.printf("%.2f", 3.2222);

Probaly there are 10 more ways of doing it, thats just what I can think of right now.

CodePudding user response：

Don't round the actual value. Let System.out.printf() do the work for you.

double [] data = {1.4452, 123.223,23.229};
for (double v : data) {
   System.out.printf("%.2f%n",v);
}

prints

1.45
123.22
23.23

CodePudding user response：

Try using the NumberFormat class. It can format the number with exact number of digits past decimal point.

CodePudding user response：

In favor for Basil's comment:

prefer BigDecimal for currency amounts

// I = PRT
// Returns: interest for n-th year for principal amount (also printed on stdout)
BigDecimal interestFor(BigDecimal principalAmount, int year) {
    BigDecimal interest = principalAmount.multiply(3*5).divide(100); // FIX:  check formula here to be correct on years!

    // Locale.US for $, but if we want Indian Rupee as: Rs
    Locale locale = new Locale("en", "IN");
    String interestFormatted = NumberFormat.getCurrencyInstance(locale).format(interest);
    
    System.out.printf("Interest for year %d is %s\n", year, interestFormatted);
    
    return interest;
}

For the placeholder literals %s (string formatted), %d (decimal formatted), see Java's Formatter syntax.