[jira] [Commented] (LANG-922) Add isOneTrue(booleans...) to BooleanUtils to preserve old behavior of BooleanUtils.xor(booleans...)

[Benedikt Ritter (JIRA)]

    [ 
https://issues.apache.org/jira/browse/LANG-922?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13795492#comment-13795492
 ] 

Benedikt Ritter commented on LANG-922:
--------------------------------------

Sample implementation:

{code:java}

    /**
     * <p>Checks if exactly one of the given booleans is true.</p>
     *
     * <pre>
     *   BooleanUtils.xor(true, true)   = false
     *   BooleanUtils.xor(false, false) = false
     *   BooleanUtils.xor(true, false)  = true
     *   BooleanUtils.xor(true, true)   = false
     *   BooleanUtils.xor(false, false) = false
     *   BooleanUtils.xor(true, false)  = true
     * </pre>
     *
     * @param array  an array of {@code boolean}s
     * @return {@code true} if the array only contained true once.
     * @throws IllegalArgumentException if {@code array} is {@code null}
     * @throws IllegalArgumentException if {@code array} is empty.
     * @since 3.2
     */
    public static boolean isOneTrue(final boolean... array) {
        // Validates input
        if (array == null) {
            throw new IllegalArgumentException("The Array must not be null");
        }
        if (array.length == 0) {
            throw new IllegalArgumentException("Array is empty");
        }

        // Loops through array, comparing each item
        int trueCount = 0;
        for (final boolean element : array) {
            // If item is true, and trueCount is < 1, increments count
            // Else, xor fails
            if (element) {
                if (trueCount < 1) {
                    trueCount++;
                } else {
                    return false;
                }
            }
        }

        // Returns true if there was exactly 1 true item
        return trueCount == 1;
    }

{code}

> Add isOneTrue(booleans...) to BooleanUtils to preserve old behavior of 
> BooleanUtils.xor(booleans...)
> ----------------------------------------------------------------------------------------------------
>
>                 Key: LANG-922
>                 URL: https://issues.apache.org/jira/browse/LANG-922
>             Project: Commons Lang
>          Issue Type: Bug
>          Components: lang.*
>            Reporter: Benedikt Ritter
>             Fix For: 3.2
>
>
> The old implementation (prior to r1532476) of BooleanUtils.xor(boolean...) 
> checked if the provided array contained exactly one boolean with value true. 
> This was changed because it is not the correct behavior for an XOR operation. 
> To preserve the behavior we should add BooleanUtils.isOneTrue(boolean...) and 
> BooleanUtils.isOneTrue(Boolean...) (and possibly the equivalents for 
> isOneFalse).



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