nextDouble(); c = scan.nextDouble(); if(a <=0 || b <= 0 || c <= 0) { System.out.println("三角形的边必须为正数"); return; } if(a + b <= c || a + c <= b || b + c <= a) { System.out.println("两边之和必须大于第三边"); return; } p = (a + b + c) /...