3条边不能构成三角形，因为三角形两边之和必须大于第三边

abstract class Shape {
abstract void calPerimeter();
}

class Triangle extends Shape {
double a, b, c;
boolean flag;

public Triangle(double a, double b, double c) {
    this.a = a;
    this.b = b;
    this.c = c;
}

public void judge() {
    if (a >= b + c || b >= a + c || c >= a + b) {
        flag = false;
    } else {
        flag = true;
    }
}

@Override
void calPerimeter() {
    if (flag == true) {
        System.out.println("长为" + a + "、" + b + "、" + c + "的3条边能构成三角形，这个三角形的周长为" + (a + b + c));
    } else {
        System.out.println("长为" + a + "、" + b + "、" + c + "的3条边不能构成三角形，因为三角形两边之和必须大于第三边");
    }
}

}

public class TriangleDemo {
public static void main(String[] args) {
Triangle t1 = new Triangle(3, 4, 5);
t1.judge();
t1.calPerimeter();
Triangle t2 = new Triangle(1, 4, 5);
t2.judge();
t2.calPerimeter();
}
}