求圆的面积（Java实现）

Java入门（2）
提示：在本章节中，将会涉及到如何通过Java实现求圆的面积！

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文章目录

• • 1.设置圆的半径
  • 2.获取圆的半径
  • 3.求圆的面积
  • 4.double类型数据保留两位小数
  • 5.汇总
  • 6.效果

1.设置圆的半径

	public void setRadius(double r) {
		this.r = r;
	}

2.获取圆的半径

	public double getRadius() {
		return this.r;
	}

3.求圆的面积

	final double PI = 3.1415926;
	double r;//半径

	public double circleArea(double r) {
		double area = 0.0;
		
		area = PI * r * r;
		
		return area;
		
	}

4.double类型数据保留两位小数

BigDecimal circleArea1_bd = new BigDecimal(circleArea1);
circleArea1_bd = circleArea1_bd.setScale(2,BigDecimal.ROUND_HALF_UP);

5.汇总

import java.math.BigDecimal;

/*
 * 计算圆的面积
 */

public class Circle {

	final double PI = 3.1415926;
	double r;//半径
	
	public void setRadius(double r) {
		this.r = r;
	}
	
	public double getRadius() {
		return this.r;
	}
	
	public double circleArea(double r) {
		double area = 0.0;
		
		area = PI * r * r;
		
		return area;
		
	}
	
	@SuppressWarnings("deprecation")
	public static void main(String[] args) {
		
		Circle  c1 = new Circle();
		
		c1.setRadius(2.5);//设置圆的半径
		
		double r1 = c1.getRadius();//获取圆的半径
		
		double circleArea1 = c1.circleArea(r1);//求圆的面积
		
		BigDecimal circleArea1_bd = new BigDecimal(circleArea1);
		circleArea1_bd = circleArea1_bd.setScale(2,BigDecimal.ROUND_HALF_UP);
		
		System.out.println("半径为"+c1.getRadius()+"的圆的面积为："+circleArea1_bd);
		
		Circle  c2 = new Circle();
		
		c2.setRadius(5);//设置圆的半径
		
		double r2 = c2.getRadius();//获取圆的半径
		
		double circleArea2 = c2.circleArea(r2);//求圆的面积
		
		BigDecimal circleArea2_bd = new BigDecimal(circleArea2);
		circleArea2_bd = circleArea2_bd.setScale(2,BigDecimal.ROUND_HALF_UP);
		
		System.out.println("半径为"+c2.getRadius()+"的圆的面积为："+circleArea2_bd);
			
	}
	
}

6.效果