/** 
 * 求三角形面积
 * */
public class Triangle {
	
	//字段，三角形三边长度
	public float firstEdge ;
	public float secondEdge ;
	public float thirdEdge ;
	
	//求三角形面积
	public void squaring() {
		//判断是否是三角形
		if( firstEdge < secondEdge + thirdEdge && secondEdge < firstEdge + thirdEdge && thirdEdge < firstEdge + secondEdge) {
			float p = (firstEdge + secondEdge + thirdEdge ) / 2 ;
			float s = p * ( p-firstEdge ) * (p-secondEdge) * (p-thirdEdge) ;
			s = (float)Math.pow(s, 0.5 ) ;
			System.out.println( "三角形面积是 ：" + s ) ;
		} else {
			System.out.println( "三条边不能构成三角形！" ) ;
		}
	}
	
	public static void main( String[] args ) {
		
		Triangle t = new Triangle() ;
		t.firstEdge = 30 ;
		t.secondEdge = 40;
		t.thirdEdge = 50 ;
		t.squaring() ;
				
	}

}