Use setRoundingMode
, set the RoundingMode
explicitly to handle your issue with the half-even round, then use the format pattern for your required output.
Example:
DecimalFormat df = new DecimalFormat("#.####");
df.setRoundingMode(RoundingMode.CEILING);
for (Number n : Arrays.asList(12, 123.12345, 0.23, 0.1, 2341234.212431324)) {
Double d = n.doubleValue();
System.out.println(df.format(d));
}
gives the output:
12
123.1235
0.23
0.1
2341234.2125
EDIT: The original answer does not address the accuracy of the double values. That is fine if you don't care much whether it rounds up or down. But if you want accurate rounding, then you need to take the expected accuracy of the values into account. Floating point values have a binary representation internally. That means that a value like 2.7735 does not actually have that exact value internally. It can be slightly larger or slightly smaller. If the internal value is slightly smaller, then it will not round up to 2.7740. To remedy that situation, you need to be aware of the accuracy of the values that you are working with, and add or subtract that value before rounding. For example, when you know that your values are accurate up to 6 digits, then to round half-way values up, add that accuracy to the value:
Double d = n.doubleValue() + 1e-6;
To round down, subtract the accuracy.
It depends on the JUnit version and what assert libraries you use.
The original answer for JUnit <= 4.12
was:
@Test(expected = IndexOutOfBoundsException.class)
public void testIndexOutOfBoundsException() {
ArrayList emptyList = new ArrayList();
Object o = emptyList.get(0);
}
Though answer https://stackoverflow.com/a/31826781/2986984 has more options for JUnit <= 4.12.
Reference :
Best Answer
In JUnit4 the exception (actually Error) thrown by a JUnit assert is the same as the error thrown by the java
assert
keyword (AssertionError), so it is exactly the same asassertTrue
and other than the stack trace you couldn't tell the difference.That being said, asserts have to run with a special flag in the JVM, causing many tests to appear to pass just because someone forgot to configure the system with that flag when the JUnit tests were run - not good.
In general, because of this, I would argue that using the JUnit
assertTrue
is the better practice, because it guarantees the test is run, ensures consistency (you sometimes useassertThat
or other asserts that are not a java keyword) and if the behavior of JUnit asserts should change in the future (such as hooking into some kind of filter or other future JUnit feature) your code will be able to leverage that.The real purpose of the assert keyword in java is to be able to turn it off without runtime penalty. That doesn't apply to unit tests.