Question

I want to make a new variable with which i can do the following:

Variable v1 = 1;
Variable v2 = "Test";
Variable v3 = 7.31;

Is this possible, or is this impossible?

Answer 1

If you take advantage of auto-boxing (Java SE 5.0 and later) then every one of those can be stored in an Object (i.e. the base class of all Java types):

public class foo {
    static public void main(String[] params) {
        Object v1 = 1;
        Object v2 = "Test";
        Object v3 = 7.31;

        System.out.println(v1 + " " + v1.getClass().getName());
        System.out.println(v2 + " " + v2.getClass().getName());
        System.out.println(v3 + " " + v3.getClass().getName());
    }
}

output:

% java foo
1 java.lang.Integer
Test java.lang.String
7.31 java.lang.Double

This does not necessarily make it a good idea, though!

The output shown above shows how although every variable was declared as an Object, their real class name is one more appropriate for their type. It’s only because every class in Java is derived from Object that the declarations can work that way.