Why doesn't my program print anything? [closed]

I am trying to make a simple Cube class and make use of StringBuilder. When I run my driver class, TestCube, nothing prints. I thought the new Cube object I created passed the integer value of '7' into the formal parameters of the Cube constructor?

Cube

StringBuilder

TestCube

Cube

Cube

Shouldn't the print statement I have print the current state of my new object (which would be 7 raised to the third power)?

package chp5;

public class Cube {

private int num1;

public Cube (int num)
{
this.num1 = (int) Math.pow (num, 3);
}


public int getnum1()
{
return num1;
}

public String toString() {
StringBuilder builder = new StringBuilder();
builder.append("That value raised to the third power is: " + num1);
return builder.toString();
}

}


package chp5;

public class TestCube {

public static void main(String args)
{
Cube testNum = new Cube(7);

System.out.println(testNum);
}
}


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