英文:
Comparing two values in Java
问题
我有两个值，我正在尝试比较它们，但结果不正确：
public void subtotal() throws Exception {
WebDriverWait wait = new WebDriverWait(session.driver, 100);
double subtotal_price = 0;
DecimalFormat decimal = new DecimalFormat("0.00");
WebElement subtotal = wait.until(ExpectedConditions.visibilityOf(element("Subtotal_cart")));
Float subtotal_value = Float.parseFloat(subtotal.getText().substring(1));
logger.info("subtotal_value" + subtotal_value);
File file = new File("ItemUPC/ItemUPC.txt");
Scanner sc = new Scanner(file);
while (sc.hasNextLine()) {
String[] line = sc.nextLine().split("[|]");
String price = line[2];
subtotal_price = subtotal_price + Double.parseDouble(price);
}
logger.info("subtotal_price" + subtotal_price);
if ((subtotal_value) == (subtotal_price)) {
logger.info("Subtotals updated");
} else {
logger.info("Subtotals not updated");
}
}
以下是ItemUPC文件：
2|BATH BENCH|19.00
203|ORANGE BELL|1.78
当我打印subtotal_price和subtotal_value的值时，我得到的都是20.78，但当在if语句中进行比较时，输出为"Subtotals not updated"。
不确定我错在哪里。有人能帮忙吗？谢谢。
英文:
I have two values and I am trying to compare them, but getting the worng results:
public void subtotal() throws Exception {
WebDriverWait wait = new WebDriverWait(session.driver, 100);
double subtotal_price = 0;
DecimalFormat decimal = new DecimalFormat("0.00");
WebElement subtotal = wait.until(ExpectedConditions.visibilityOf( element("Subtotal_cart")));
Float subtotal_value = Float.parseFloat(subtotal.getText().substring(1));
logger.info("subtotal_value"+subtotal_value);
File file = new File("ItemUPC/ItemUPC.txt");
Scanner sc = new Scanner(file);
while (sc.hasNextLine()) {
String[] line = sc.nextLine().split("[|]");
String price = line[2];
subtotal_price = subtotal_price + Double.parseDouble(price);
}
logger.info("subtotal_price"+subtotal_price);
if ((subtotal_value)==(subtotal_price))
{
logger.info("Subtotals updated");
}
else
{
logger.info("Subtotals not updated");
}
}
The following is the ItemUPC file:
2|BATH BENCH|19.00
203|ORANGE BELL|1.78
When I print the value of subtotal_price and Subtotal_value I am getting both as 20.78, but when its getting compared in the if statement, I am getting output as "Subtotals not updated"
Not sure where I am getting wrong. Can someone please help? Thank you.
答案1
得分: 3
比较浮点数可能会很有挑战性，这是由于浮点类型之间精度的差异，以及它们对十进制数字的二进制表示之间的差异。
你有两个简单的选择：
- 将两个值之间的差的绝对值与 epsilon（阈值）值进行比较
- 使用
BigDecimal作为替代你的Float和double变量类型
示例 1：
// 可能会在某些边缘情况下失败的简化
static final double EPSILON = .001; // 可接受的误差 - 根据需求进行调整
if (Math.abs(subtotal_price - subtotal_value) < EPSILON) {
logger.info("Subtotals updated");
}
// ...
示例 2：
BigDecimal subtotal_price = new BigDecimal("0");
// ...
BigDecimal subtotal_value = new BigDecimal(subtotal.getText().substring(1));
// ...
if(subtotal_price.compareTo(subtotal_value) == 0) {
logger.info("Subtotals updated");
}
// ...
英文:
Comparing floating point numbers can be challenging, due to differences in precision between floating point types and their binary representations of decimal numbers.
You have two simple options:
- Compare the absolute value of the difference between the two values to an epsilon, or threshold, value
- Use
BigDecimalas a substitute for yourFloatanddoublevariable types
Example 1:
// simplification that may fail in certain edge cases
static final double EPSILON = .001; // acceptable error - adjust to suit your needs
if (Math.abs(subtotal_price - subtotal_value) < EPSILON) {
logger.info("Subtotals updated");
}
// ...
Example 2:
BigDecimal subtotal_price = new BigDecimal("0");
// ...
BigDecimal subtotal_value = new BigDecimal(subtotal.getText().substring(1));
// ...
if(subtotal_price.compareTo(subtotal_value) == 0) {
logger.info("Subtotals updated");
}
// ...
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