Calculating the distance between 2 given points

I have to create a class to calculate the distance between 2 given points for class. The instructor gave us the top half of the assignment with all the necessary code without modifying, the problem that im having is creating the class part. This is what i have so far...

class Point{
int x;
int y;

public Point(){
    this.x = 0;
    this.y = 0;

}

public Point(int x, int y){
    this.x = x;
    this.y = y;
}
 public double distance(int x, int y) {
    double d = Math.sqrt( Math.pow(x2-x1, 2) + Math.pow(y2-y1, 2) );
    return distance;
}
}

the top half of the assignment looks like this:

import java.util.Scanner;


class Assignment4{
public static void main(String[] args){
    // first and second points
    Point first, second;

    // try parsing points from command line args
    if(args.length==4){
        // new Point(int x, int y) creates a new Point located at position (x,y)
        first = new Point(Integer.valueOf(args[0]), Integer.valueOf(args[1]));
        second = new Point(Integer.valueOf(args[2]), Integer.valueOf(args[3]));
    }

    // if not specified as argument, get points from user
    else{
        Scanner input = new Scanner(System.in);

        System.out.println("Enter first point: ");
        first = new Point(input.nextInt(),input.nextInt());

        System.out.println("Enter second point: ");
        second = new Point(input.nextInt(),input.nextInt());
    }

    //calculate distance
    //double d = Math.sqrt( Math.pow(x2-x1, 2) + Math.pow(y2-y1, 2) );
    double d = first.distance(second.x, second.y);

    System.out.println("Distance between " + 
        "(" + first.x + "," + first.y + ")" + 
        " and " + 
        "(" + second.x + "," + second.y + ")" + 
        " is " + d);
    System.out.println();
}
}

When i try and compile the program, it says "cannot find symbol" referring to x2, x1, y2, y1, and distance.