java ， 用单元格计算圆环的面积， 使用FOR 循环的~求高手啊！！有伪代码，求怎么用java写~

BEGIN Area of Annulus
Set gridSize = 20 (we could use 20 by 20 grid cells)
Get r1 from user (outer radius)
Get r2 from user (inner radius)
Set minx = -r1
Set maxx = r1
Set miny = -r1
Set maxy = r1
Set counter = 0 (will count how many grid cells are on the annulus)
For column = 0 to gridSize-1
Set x = minx + (column + 0.5)*((maxx–minx)/gridSize)
For row = 0 to gridSize-1
Set y = miny + (row + 0.5)*((maxy–miny)/gridSize)
Set test = x*x + y*y
if test < r1*r1 and test > r2*r2
Set counter = counter + 1
Set area = (maxx-minx)*(maxy-miny)*counter/(gridSize * gridSize)
Output “Area : ” area
END Area of Annulus

补充：高手快来啊。。。求助 求助！！！！！！

答案：现在的好多了

public class TestManager {
	public static void main(String[] args) {
		areaOfAnnulus(6.5, 3.2);
		areaOfAnnulus2(6.5, 3.2);
                                areaOfAnnulus(26.5, 3.2);
		areaOfAnnulus2(26.5, 3.2);
	}

	/**
	 * 用单元格计算圆环的面积
	 * 
	 * @param r1
	 *            外圆半径
	 * @param r2
	 *            内圆半径
	 */
	public static void areaOfAnnulus(double r1, double r2) {
//		int gridSize = 20;
		double minx = -r1;
		double maxx = r1;
		double miny = -r1;
		double maxy = r1;
		long gridSize = Math.round(r1/0.5);
		int counter = 0;
		for (int column = 0; column <= gridSize-1; column++) {
			double x = minx + (column + 0.5) * ((maxx - minx) / gridSize);
			for (int row = 0; row <= gridSize-1; row++) {
				double y = miny + (row + 0.5) * ((maxy - miny) / gridSize);
				double test = x * x + y * y;
				if (test < r1 * r1 && test > r2 * r2) {
					counter++;
				}
			}
		}
		double area = (maxx - minx) * (maxy - miny) * counter
				/ (gridSize * gridSize);
		System.out.println("area:" + area);
	}
	
	/**
	 * 外圆减内圆面积
	 * @param r1 外圆半径
	 * @param r2 内圆半径
	 */
	public static void areaOfAnnulus2(double r1, double r2) {
		System.out.println("area:" + Math.PI*(r1*r1-r2*r2));
	}
}

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