== isn’t equals, or is it?

Beware of the subtle differences of == and equals in Java and Groovy.

== and equals behave different in Java (and Groovy). You all know the subtle difference when it comes to comparing strings. equals is recommended in Java, == works in Groovy, too. So you could think that using equals is always the better option… think again!
Take a look at the following Groovy code:

  String test = "Test"
  assertTrue("Test" == test) // true!
  assertTrue("Test" == "${test}") // true!
  assertTrue("Test".equals("${test}")) // false?!

The same happens with numbers:

  assertTrue(1L == 1) // true!
  assertTrue(1L.equals(1)) // false?!

A look at the API description of equals shows the underlying cause (taken from the Integer class):

Compares this object to the specified object. The result is true if and only if the argument is not null and is an Integer object that contains the same int value as this object.

equals follows the contract or best practice (see Effective Java) that the compared objects must be of the same class. So comparing different types via equals always results in false. You can convert both arguments to the same type beforehand to ensure that you get the expected behavior: the comparison of values. So next time when you compare two values think of the types or convert both values to the same type.

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