Error : Main method not found in java class

Question

I am new to concepts of java. while preparing my first program of classes with objects i encountered a problem. here is the code and the error..please resolve.. PROGRAM:

class Fact
{
    private int i;
    private int n;
    private int fact;

    public Fact()
        { fact=1;
          i=1;
        }
    public Fact( int x)
        { n=x; }
    public void getAnswer()
        {
            while(i<=n)
            {fact=fact*i;
                i++;}
            System.out.println(fact);
        }
}
class FactMain
{
    public static void main(String dt[])
    {
    Fact obj= new Fact(6);
    obj.getAnswer();
    }
}

ERROR:

Main method not found in class Fact, please define the main method as:
public static void main(String[] args)

Answer 1

Rename the class file name Fact.java to FactMain.java.

private int fact;

public Fact()
    { fact=1;
      i=1;
    }
public Fact( int x)
    { n=x; }

Note, your default constructor set fact but constructor Fact( int x) set n. Hence fact is 0. So your output is 0 too.

Solution:

public Fact(int x) {
    fact = 1;
    i = 1;
    n = x;
}

Or,

public Fact(int x) {
    this(); // default constructor
    n = x;
}

Here is the complete solution:

Create a single class file named FactMain.java, then paste the following code:

class Fact {
    private int i;
    private int n;
    private int fact;

    public Fact() {
        fact = 1;
        i = 1;
    }

    public Fact(int x) {
        this();
        n = x;
    }

    public void getAnswer() {
        while (i <= n) {
            fact = fact * i;
            i++;
        }
        System.out.println(fact);
    }
}

class FactMain {
    public static void main(String[] dt) {
        Fact obj = new Fact(6);
        obj.getAnswer();
    }
}