# Thread: java program help. find the radius of a circle

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Feb 2009
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## java program help. find the radius of a circle

I have a java program I need to complete, but I don't know how to prompt the user. I've done a little bit already (if that helps). below is my assignment and below that is what I've done myself.

The following formula gives the distance between two points (x1, y1) and (x2, y2) in the Cartesian plane:

sqrt (x2-x1)^2 + (y2-y1)^2

Given the center and a point on a circle, you can use this formula to find the radius of a circle. Write a program that prompts the user to enter the center and a point on the circle. The program should then output the circles radius, diameter, circumference, and area. Your program must have at least the following methods:

a. distance: This method takes as its parameters four numbers that represent two points in the plane and returns the distance between them.
b. Radius: This method takes as its parameter four numbers that represent the center and a point on the circle, calls the method distance to find the radius of the circle, and returns the circles radius.
c. Circumference: This method takes as its parameter a number that represents the radius of the circle and returns the circles circumference. (if r is the radius, the circumference is 2(Pi)r.)
d. Area: This method takes as its parameter a number that represents the radius of the circle and returns the circles area. (If r is the radius, the area is (Pi)r^2.)
e. Assume that Pi =3.1416

what I've done

public class Circle {

public static void main (String sdfsf[])
{
double radius = getRadius(3, 0, 0, 4);
System.out.println(radius);

double circumference = getCircumference(radius);
System.out.println(circumference);

double area = getArea(radius);
System.out.println(area);
}

static private double getRadius (double centerx, double centery, double x1, double x2)
{
return getDistance(centerx, centery, x1, x2);
}

static private double getDistance (double x1, double y1, double x2, double y2)
{
return Math.sqrt((x2-x1)*(x2-x1) + (y2-y1)*(y2-y1));
}

static private double getCircumference(double radius)
{
return 2*Math.PI*radius;
}  Reply With Quote

2. ## Your prompt the user for the input in thsi way:
Java Code:
```Scanner scan =new Scanner(System.in);
System.out.println("Enter the radius");
int userInput=scan.nextInt();
System.out.println("You entered: "+userInput);```
Before you declare the class import library:

Java Code:
`import java.util.*;`  Reply With Quote

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