Java - what does "(Customer) v.get(i)" do?

Question

I'm new to java, I have the code below (v is a vector) and I don't understand this:

(Customer) v.get(i)

Please explain to me .tks

public void insert(Customer c) {
    boolean checkExist = true;
    if (checkExist && !isIn(c,v)) {
        for (int i = 0; i < v.size(); i++) {
            int check = c.compareTo((Customer) v.get(i));
            if (check < 0) {
                Customer x = new Customer();
                x = (Customer) v.get(i);
                v.set(i, c);
                c = x;
            }
        }
        v.add(c);
    }
}
public boolean isIn(Customer c, Vector els) {
    c = new Customer();
    for (int i = 0; i < els.size(); i++) {
        if (c.equals(els.get(i))) {
            return true;
        }
    }
    return false;
}

You almost certainly don't want the `c = new Customer();` line. It overwrites the value that you are passing in as a parameter; you may as well not pass in `Customer c` at all. — Andy Turner, Nov 19 '15 at 17:37
http://stackoverflow.com/questions/5289393/casting-variables-in-java — Sotirios Delimanolis, Nov 19 '15 at 17:41
http://stackoverflow.com/questions/5306835/casting-objects-in-java — Sotirios Delimanolis, Nov 19 '15 at 17:41

score 0 · Answer 1 · answered Nov 19 '15 at 17:36

0

v.get(i) gets the ith member of v, and (Customer) casts it to a Customer class.

See the tutorial, "Casting Objects."

answered Nov 19 '15 at 17:36

markspace

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score 0 · Answer 2 · answered Nov 19 '15 at 17:36

It is casting the object returned by v.get(i) to a Customer, so the object returned can be treated as a Customer, accessing methods in the Customer class/interface. If the object returned cannot be cast to a Customer, because it does not extend/implement Customer, it will throw a ClassCastException.

Nir Alfasi · Accepted Answer · 2015-11-19T17:53:09.683

You don't show us how v is declared.

In the following two lines there's a harmless bug:

Customer x = new Customer();
x = (Customer) v.get(i);

On the first line a new Customer object is created, but it's never being used, and after the assignment on the following line - this object is eligible to garbage-collection.

These two lines can be substituted by:

Customer x = (Customer) v.get(i);

The reason there is a need to use casting (Customer) is in case v is declared to hold a more general type object, and we need to cast it to Customer in order to assign it to x and use Customer properties and methods.

For more about casting see Casting Objects section.

score 0 · Answer 4 · answered Nov 19 '15 at 17:38

0

x = (Customer) v.get(i);

Means that your typecasting the i-element from your vector to the class Customer. In simpler words making v.get(i) of the type Customer.

answered Nov 19 '15 at 17:38

Møssi

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Java - what does "(Customer) v.get(i)" do?

4 Answers4