Java code: Limiting float values to 2 points past decimal.

[semisonic9]

I'm trying to figure out how to limit a float output to two points past the decimal.

import java.util.Scanner;

public class Land {

public static void main(String[] args) {

int length, width;
float acreage;

Scanner keyboard = new Scanner(System.in);

System.out.println("Please enter the length, in feet, of the length of a piece of land.");
length = keyboard.nextInt();
System.out.println("Please enter the length, in feet, of the width of a piece of land.");
width = keyboard.nextInt();

acreage = (length * width) / 43560;
System.out.println("Your acreage is " + acreage);
}
}

And I need the acreage only to two decimal places. Having a devil of a time trying to figure out how to make that happen.

I also need to know how to have it round up or down, as appropriate, for situations handling money.

 

[pat1006]

try ((int)(acreage*100+0.5)) / 100.0

(untested)

 

[devman]

See java.math.BigDecimal and related class java.math.MathContext for arbitrary precision math.

 

[LuminaryJanitor]

Take a look at the DecimalFormat class.

 

[DrFreeze]

if i remember correctly, NumberFormat allows you to set the min and max amount of decimals when formatting a number

IE:

NumberFormat nf = NumberFormat.getInstance();
nf.setMaxFractionDigits(2);
nf.setMinFractionDigits(2);
System.out.println(nf.format(3.1415));

this will output '3.14'

 

[Xeno8]

You want printf. Here's some example code:

float value = 1234.56789f;
System.out.printf("%.2f", value);   // Prints "1234.57"

Incidentally, there's an expression in your code that's just begging for trouble:

acreage = (length * width) / 43560;

Since all values in the expression are integers, integer division (case 4) will be performed. You want floating-point division. So, either make length or width floats, or divide their product by "43560f", not "43560".

 

[devman]

3 different ways to achieve the same result!

Using a NumberFormat object is probably the way you want to go if you just need to display the result and do not need to do a bunch of computations on it.

 

[Whatsisname]

achieve it through when its displayed, don't get carried away trying to limit yourself to 2 decimal point precision math or some similar nonsense.

 

[semisonic9]

Incidentally, there's an expression in your code that's just begging for trouble:

acreage = (length * width) / 43560;

Since all values in the expression are integers, integer division (case 4) will be performed. You want floating-point division. So, either make length or width floats, or divide their product by "43560f", not "43560".

Nice catch.

Went with DecimalFormat class on this one. Thanks for the feedback!