Difference between String equals and

Question

I have the below code, in which I have a string which I am breaking down into tokens and storing them into an array of String afterward. Then I am trying to compare the first array with a variable using == but it's not giving me any output but when I am using String.equals() it is giving me the result. So, can someone explain me the difference between String.equals and ==?

public static void main(String...aArguments) throws IOException {

    String userId = "Andrew";
    String password = "236475";

    String userData = "Andrew 236475";
    StringTokenizer tokens = new StringTokenizer(userData, " ");
    int n_uData = tokens.countTokens();
    String[] u_Data = new String[n_uData];
    int i = 0;

    while (tokens.hasMoreTokens()) {
        String str = tokens.nextToken();
        u_Data[i] = str;
        i++;
    }

    //System.out.println (userId);

    if ((u_Data[0] == userId)) {
        System.out.println("WORKING");
    }
}

Answer 1

Though both are used for comparison, but the way they both works are pretty much different.

== is called the comparison operator. This compares the references of the operands, that is the physical address in which the variables are stored. It returns true if and only if both variables refer to the same object.

String.equals() is a pre-built function of String class which compares the values stored in the objects. It checks nothing except for the value specified in the function.

Thus in your code when you are using == it is comparing the reference of userId and u_id whereas when using equals() it is comparing the values stored in them.