how to convert integer to bigdecimal in java

Question

I want to create a method that caculates multiplication an integer and a bigdecimal. I search on google and forums nothing I found.

import java.math.BigDecim         


        

Answer 1

To multiply an integer (or byte/short/float/double) with a BigInteger (or BigDecimal), you must convert the native number to BigInteger/BigDecimal first.

// int parameter can be int or Integer
public static BigInteger multiply ( int a, BigInteger b ) {
   return BigInteger.valueOf( a ).multiply( b );
}

// BigInteger <> BigDecimal
public static BigDecimal multiply ( int a, BigDecimal b ) {
   return BigDecimal.valueOf( a ).multiply( b );
}

// same for add, subtract, divide, mod etc.

Note: valueOf is not the same as new, and for different reasons on BigDecimal and BigInteger. In both cases, I recommend valueOf over new.

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I see that you added your code, nice. It doesn't work because Integer is mixed with BigDecimal, and also * does not work with BigDecimal. If you compare it with my code, the fix should be obvious:

public BigDecimal methCal ( int quantite, BigDecimal prixUnit ) {
    return BigDecimal.valueOf( quantite ).multiply( prixUnit );
}

Answer 2

Try this:

import java.math.*;

public class calculator{

    public static void main(String[] args) {

        BigDecimal value1 = new BigDecimal("3383878445");
        BigDecimal returnValue = calculation(2,value1);
        System.out.println("value is :" + returnValue);
    }

   public static BigDecimal calculation(int no1, BigDecimal no2){
        BigDecimal value = BigDecimal.valueOf(no1).multiply(no2);
        return value;
    }
}

Answer 3

These methods from the Java API will be helpful.

public BigDecimal multiply​(BigDecimal multiplicand)

Returns a BigDecimal whose value is (this × multiplicand), and whose scale is (this.scale() + multiplicand.scale()).

Parameters: multiplicand - value to be multiplied by this BigDecimal. Returns: this * multiplicand

public BigDecimal​(int val)

Translates an int into a BigDecimal. The scale of the BigDecimal is zero.

Parameters: val - int value to be converted to BigDecimal.

Answer 4

Google definitely could have helped you, if you know what to look for:

https://docs.oracle.com/javase/9/docs/api/java/math/BigDecimal.html#BigDecimal-int-

This is one of the constructors for BigDecimal, which allows you to do the following:

BigDecimal five = BigDecimal.valueOf(5);
BigDecimal seven = BigDecimal.valueOf(2).add(five);

Seeing as you stated you wanted to multiply an int and a BigDecimal, this would be achieved as follows:

BigDecimal result = yourBigDecimal.multiply(BigDecimal.valueOf(yourInt));

And, supposing you want this result as an int:

int intResult = result.intValue();

Keep in mind that this throws away the fraction though. If you want rounding instead:

int intResult = result.round(0, RoundingMode.HALF_UP).intValue();