package org.metaborg.util.arrays;

import java.util.Collection;

public final class Arrays2 {
    public static <T> boolean addAll(Collection<T> addTo, T[] elementsToAdd) {
        boolean modified = false;
        for(T e : elementsToAdd) {
            modified = addTo.add(e) || modified;
        }
        return modified;
    }
}

package org.metaborg.util.arrays;

import java.util.Collection;

public final class Arrays2 {
    public static <T> boolean addAll(Collection<T> addTo, T[] elementsToAdd) {
        boolean modified = false;
        for(T e : elementsToAdd) {
            modified = modified || addTo.add(e);
        }
        return modified;
    }
}

--- 
+++ 
@@ -6,7 +6,7 @@
     public static <T> boolean addAll(Collection<T> addTo, T[] elementsToAdd) {
         boolean modified = false;
         for(T e : elementsToAdd) {
-            modified = modified || addTo.add(e);
+            modified = addTo.add(e) || modified;
         }
         return modified;
     }
Fix only one element being added.
