Given that an object is an array of any type, how to test that it is empty in Java?

Please help me fill in my isempty method:

public static boolean isEmpty(Object test){
    if (test==null){
        return true;
    }
    if (test.getClass().isArray()){
        //???
    }
    if (test instanceof String){
        String s=(String)test;
        return s=="";
    }
    if (test instanceof Collection){
        Collection c=(Collection)test;
        return c.size()==0;
    }
    return false;
}

What code will I use to determine if I am processing an array and if its length is zero, it will return true? I want it to work, whether the type is int [], object [] (just you know, I can tell you that if you put an int [] into an object [] variable, it will throw an exception.)

Solution

You can use Java reflect. Helper method getlength (object) in array:

public static boolean isEmpty(Object test){
    if (test==null){
        return true;
    }
    if (test.getClass().isArray()){
        return 0 == Array.getLength(test);
    }
    if (test instanceof String){
        String s=(String)test;
        return s.isEmpty(); // Change this!!
    }
    if (test instanceof Collection){
        Collection c=(Collection)test;
        return c.isEmpty();
    }
    return false;
}

Please note that you cannot use

boolean empty = (someString == "");

Because it's not safe To compare strings, use string Equals (string), or in this case, just check if the length is zero