In Java, arrays are objects and support object methods such as Object.equals()
. However, arrays do not support any methods besides those provided by Object
. Consequently, using Object.equals()
on any array only compares array references rather than their contents. Programmers who wish to compare the contents of two arrays must use the static two-argument Arrays.equals()
method. This method considers two arrays equivalent if both arrays contain the same number of elements, and all corresponding pairs of elements in the two arrays are equivalent, according to Object.equals()
. In other words, two arrays are equal if they contain equivalent elements in the same order. To test for reference equality, use the reference equality operators, ==
and !=
. To test for content equality, use Object.equals()
.
Because the effect of using Object.equals()
to compare two arrays is often misconstrued as content equality, and because a better alternative exists in the use of reference equality operators, the use of the Object.equals()
method to compare two arrays is disallowed.
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Bibliography
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EXP01-J. Never dereference null pointers 02. Rule 02: Expressions (EXP)