Apache下commons-lang工具包下BooleanUtils类的xor(true, true, true)结果为false，为什么？

Question

The result of xor(true, true, true) of the BooleanUtils class under the commons-lang toolkit under Apache is false , but the result of System.out.println(true ^ true ^ true) is true . Why?

    public class Test {
    public static void main(String[] args) {
        System.out.println(org.apache.commons.lang.BooleanUtils.xor(new boolean[]{true, true, true}));
        System.out.println(org.apache.commons.lang3.BooleanUtils.xor(new boolean[]{true, true, true}));
        System.out.println(true ^ true ^ true);
    }
}
/*
    打印结果：
        false
        false
        true
 */

Answer 1

The most likely reason you are seeing this behavior is that you are using an older version of commons-lang (< 3.2).

Newer versions behave the same as Java (ie it evaluates one xor at a time from left to right).

The older versions used a different approach however: They return true only if there is exactly one true value in the entire array.

This behavior was considered incorrect (see LANG-921 ) and has since been fixed.