CODEWITHSUNDEEP
javastringassert
Miervatea
Miervatea

Reputation: 63

Assert the String has certain length (Java)

Is there any way to assert in a method that input String has certain length?

I tried assert stringName[4]; but seems like it doesn't work

Upvotes: 4

Views: 13548

Answers (4)

hertzsprung
hertzsprung

Reputation: 9893

Use AssertJ hasSize():

assertThat(stringName).hasSize(4)

Upvotes: 3

Gabriel Furstenheim
Gabriel Furstenheim

Reputation: 3432

If you are using hamcrest, then you can do:

 assertThat("text", hasLength(4))

See http://hamcrest.org/JavaHamcrest/javadoc/2.2/ > CharSequenceLength

Good thing about this is that it will have a proper error message, among others including the string itself.

Upvotes: 0

ayushgp
ayushgp

Reputation: 5091

If you just want to use the Java's assert keyword and not any library like JUnit, then you can probably use:

String myStr = "hello";
assert myStr.length() == 5 : "String length is incorrect";

From the official docs:

The assertion statement has two forms. The first, simpler form is:

assert Expression1;

where Expression1 is a boolean expression. When the system runs the assertion, it evaluates Expression1 and if it is false throws an AssertionError with no detail message.

The second form of the assertion statement is:

assert Expression1 : Expression2 ;

where: Expression1 is a boolean expression. Expression2 is an expression that has a value. (It cannot be an invocation of a method that is declared void.)

You can use the following if you're using a testing library like JUnit:

String myStr = "hello";
assertEquals(5, myStr.length());

Update: As correctly pointed out in the comments by AxelH, after compilation, you run the first solution as java -ea AssertionTest. The -ea flag enables assertions.

Upvotes: 7

Hearen
Hearen

Reputation: 7828

Instead of using assert, I'd recommend using Exception to check the state of the variables as a simple demo:

String[] arr = new String[3];
if (arr.length != 4) {
    throw new IllegalStateException("Array length is not expected");
}

This will directly give the hint by exceptions and you don't need to bother with assert in jvm options. 

Exception in thread "main" java.lang.IllegalStateException: Array length is not expected
    at basic.AssertListLength.main(AssertListLength.java:7)

Upvotes: 0

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