Question

I am working with Hashtable in my java program. I just surprised by seeing the abnormal behavior of Hastable. Below is my code (This is not my final code, i simply created a new simple project with the code which is running abnormal)

    Hashtable<char[], char[]> h1 = new Hashtable<char[], char[]>();
    char[] key = Integer.toString(12).toCharArray();
    char[] val = Integer.toString(21).toCharArray();
    h1.put(key, val);
    System.out.println(h1.containsKey(Integer.toString(12).toCharArray()));// Should print true, since 12 is there in Hashtable

Answer 1

You can’t use arrays like this as map keys, because arrays have the default, referential-equality-based Object implementations of equals and hashCode. Using String as the key instead would make your program work as desired.