1. Constructors are special methods that are called when creating an object using the new operator. They do not have a return type. 2. An array's default element values are 0 for numeric, false for boolean, '\u0000' for char, and null for object types. 3. Passing objects to methods passes the reference by value, so changes to the object within the method are reflected outside, but reassigning the reference does not swap the objects.