java 添加到 BigDecimal 时出现 NullPointerException
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NullPointerException when adding to BigDecimal
提问by Dan
String[] toppings = new String[10];
BigDecimal toppingsPrice = null;
toppings[0] = req.getParameter("extraCheese");
toppings[1] = req.getParameter("moreTomatoes");
toppings[2] = req.getParameter("extraOnions");
// ...
for(int i = 0; i < toppings.length; i++) {
if(toppings[i] != null) {
toppingsPrice.add(new BigDecimal("0.99")); // <-- NPE is caused here.
toppingsPrice = toppingsPrice.setScale(2, BigDecimal.ROUND_HALF_EVEN);
}
}
I am getting a NullPointerExceptionin the above code when adding 0.99to toppingsPrice. I am working with money values, so I have used BigDecimal. Is there something wrong with how I am adding the 0.99c price?
我得到一个NullPointerException加时在上面的代码0.99来toppingsPrice。我正在处理货币价值，所以我使用了BigDecimal. 我添加 0.99c 的价格有什么问题吗？
回答by Tudor
You are setting toppingsPriceto null and never changing it to point to something:
您将设置toppingsPrice为 null 并且永远不会将其更改为指向某些内容：
BigDecimal toppingsPrice = null;
...
toppingsPrice.add(new BigDecimal("0.99"));
Did you mean
你的意思是
BigDecimal toppingsPrice = new BigDecimal(0);
回答by gkamal
You need to initialize toppingsPrice
您需要初始化 toppingsPrice
change this line
改变这一行
BigDecimal toppingsPrice = null;
to
到
BigDecimal toppingsPrice = new BigDecimal(0);
回答by malina
If you would have a look at API you would see that :
如果您看一下 API，您会看到：
add(BigDecimal augend)
添加（BigDecimal 被加数）
Returns a BigDecimal whose value is (this + augend), and whose scale is max(this.scale(), augend.scale()).
返回一个 BigDecimal，其值为 (this + augend)，其比例尺为 max(this.scale(), augend.scale())。
