是否有可能制作一种可能是不同的新变量？

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 (ie 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.

Answer 2

It is possible. Check the code below:

    Object a;
    Object b;
    Object c;

    a = 1;
    b = "abc";
    c = 1.72d;

or another way:

    Object a;

    a = 1;
    a = "abc";
    a = 1.72d;

In this case we observe autoboxing , when a value is wrapped to a suitable object type.

As Object class is the parent for all java objects, then we have a way to code as I described above.