如何在java中将整数转换为bigdecimal

how to convert integer to bigdecimal in java

提问by ema

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

我想创建一个计算乘法整数和大十进制的方法。我在谷歌和论坛上搜索我没有找到任何东西。

import java.math.BigDecimal;
private Integer quantite;
private BigDecimal prixUnit;

public Integer getQuantite() {
        return quantite;
    }

    public void setQuantite(Integer quantite) {
        this.quantite = quantite;
    }


    public BigDecimal getPrixUnit() {
        return prixUnit;
    }

    public void setPrixUnit(BigDecimal prixUnit) {
        this.prixUnit = prixUnit;
    }

public BigDecimal methCal(BigDecimal quantite, BigDecimal prixUnit){

        this.prixUnit=prixUnit;
        BigDecimal j = new BigDecimal(quantite);
        this.j = quantite;

        return quantite*prixUnit ;
}

Can someone help me?

有人能帮我吗？

采纳答案by Sheepy

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

要将整数（或字节/短整数/浮点数/双精度数）与 BigInteger（或 BigDecimal）相乘，您必须先将本机数转换为 BigInteger/BigDecimal。

// 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: valueOfis not the same as new, and for different reasons on BigDecimaland BigInteger. In both cases, I recommend valueOfover new.

注意：valueOf是不一样的new，而且在不同的原因的BigDecimal和BigInteger的。在这两种情况下，我都推荐valueOf超过new.

---

---

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:

我看到你添加了你的代码，很好。它不起作用，因为 Integer 与 BigDecimal 混合，并且*也不适用于 BigDecimal。如果将其与我的代码进行比较，则修复应该很明显：

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

回答by Jeroen Steenbeeke

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

如果您知道要查找的内容，Google 绝对可以帮助您：

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

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:

这是 BigDecimal 的构造函数之一，它允许您执行以下操作：

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:

正如您所说，您想将一个 int 和一个 BigDecimal 相乘，这将按如下方式实现：

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

And, supposing you want this result as an int:

并且，假设您希望此结果为 int：

int intResult = result.intValue();

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

请记住，这会丢弃分数。如果你想要四舍五入：

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

回答by Imal

These methods from the Java API will be helpful.

Java API 中的这些方法会很有帮助。

public BigDecimal multiply?(BigDecimal multiplicand)

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

返回一个 BigDecimal，其值为 (this × multiplicand)，其比例为 (this.scale() + multiplicand.scale())。

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

参数： multiplicand - 要与此 BigDecimal 相乘的值。返回：这个 * 被乘数

public BigDecimal?(int val)

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

将 int 转换为 BigDecimal。BigDecimal 的标度为零。

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

参数： val - 要转换为 BigDecimal 的 int 值。

回答by Minoli Alles

Try this:

尝试这个：

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;
    }
}