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Arbitrary amount of decimals while dividing [closed]

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I'm new to programming. I have a task to make a division of two arbitrary numbers, and to set arbitrary number of decimals. I was searching on the internet, but not really sure how to set it. If I could get some help, would much appreciate!
Here's the code so far:
int a,b, decimala;
System.out.println("first number: ");
a = unos.nextInt();
System.out.println("second number: ");
b = unos.nextInt();
System.out.println("amount of decimals: ");
decimala = unos.nextInt();
double c;
System.out.println(a);
System.out.println(b);
System.out.println("--------------");
c = (double)a/b;
System.out.println(%.decimala+ c);

If you just want to output them you could try using format
String format = "%" + decimala + "f";
System.out.format(format,a);
Here's a cheat sheet with all the stuff you can do.
https://alvinalexander.com/programming/printf-format-cheat-sheet
Thanks to #AndrewGuerra for pointing out how to format a variable amount of decimals

Put point in string value (android java) [closed]

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I have BMI calculator app that takes some input and puts it in "EditText". Here is what I am trying to do:
If the input is 170, it will become 1.70.
If the input is 1.70, it will not change.
This is the code I have:
String weight = editText.getText().toString();

Cant you convert the string to an integer and take modulus 100 to the cms and divide by 100 to get in meters?
You can convert the String weight to int like this
int wgt = Integer.parseInt(weight);
Then separating meters and centimetres.
int mtrs = wgt / 100;
int cms = wgt % 100;
Then combining both
String result = mtrs + "." + cms;

try something like this
float value = Float.parse("170");
editText.setText(String.Format(Locale.ENGLISH,"%,02f", value/100f))

I found this way works: I take the number that the user put, and then "170/100" + "0" gives me 1.70

Function floor of BigInteger [closed]

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I'm looking for a function such as Math.floor(int x) but for a variable of type BigInteger. Does anyone know how to do it?

Let's suppose a and b are int variables. In that case a/b is an int. Test case:
int a = 5;
int b = 2;
System.out.println(a / b); //expected output is 2
Let's suppose a and b are integers, but we intend to convert the result of the division into a float. The result depends on the way of conversion. Test case:
int a = 5;
int b = 2;
System.out.println((float)(a / b)); //expected output is 0.0
System.out.println(((float)a) / b); //expected output is 2.5
Let's suppose a and b are BigInteger variables. a.divide(b) will return a BigInteger value (so floor is not needed) unless b is 0 in which case it will throw an exception. Source.

How to change 15% into 0.15 in Java? [closed]

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So, I am making a basic tip calculator and I need to know how to change the users input of 15%, 23%, etc. into 0.15, 0.23, etc.
This is my current code:
import java.util.Scanner;
public class TipCalc {
public static void main(String args[]) {
Scanner meal = new Scanner(System.in);
double food, tax, tip, fin;
System.out.println("How much was the meal?");
food = meal.nextDouble();
System.out.println("How much was the tax?");
tax = meal.nextDouble();
System.out.println("How much would you like to tip? I recomend 15%");
tip = meal.nextDouble();
}
}
Please help! Thanks!

double tip;
tip = meal.nextDouble() / 100;
Or
double tip = 15.0;
tip = tip / 100;
Or Even
double tip = 15.0;
tip /= 100;

If the input for your tip is 15.
Using
tip = meal.nextDouble() / 100.0;
System.out.println(tip);
would OUTPUT: 0.15

DecimalFormat Spaghetti [closed]

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First time using the DecimalFormat classes...
I need to store 4 decimals precision for my value.
Let me show you what I have done so far.
public class Paper
{
public String name, color, type,finish,grain;
public double width,height,gsm, lbs,ppi;
public DecimalFormat df;
public Paper()
{
String pattern = "#0.0000";
df = new DecimalFormat(pattern);
}
public void setWidthAndHeight(String width, String height)
{
//I've censured what I tried so far.
///I need to ensure that the passed width has 4 decimals and that it is stored that way.
this.width = //ENTER answer here! :)
}
Thank you for your time, and patience.

You can use BigDecimal to manage your decimals.
BigDecimal n = new BigDecimal("100.12345");
n = n.setScale(4, RoundingMode.HALF_UP);
n = n.stripTrailingZeros();
System.out.println(n.toPlainString());
Using scale will round your number to 4 decimal precision. Remove any zeros using stripTrailingZeros and use toPlainString to get your number later for printing.
http://docs.oracle.com/javase/7/docs/api/java/math/BigDecimal.html