以++为例
int i = 5;
i++; 先取值，再运算
++i; 先运算，再取值

public class HelloWorld {
public static void main(String[] args) {
int i = 5;
System.out.println(i++); //输出5
System.out.println(i); //输出6

int j = 5;
System.out.println(++j); //输出6
System.out.println(j); //输出6
}
}

BMI的计算公式是 体重(kg) / (身高*身高)

比如邱阳波的体重是72kg, 身高是1.69，那么这位同学的BMI就是
72 / (1.69*1.69) =

import java.util.Scanner;
public class A {
public static void main(String[] args) {
Scanner reader = new Scanner(System.in);
System.out.print("请输入您的体重:"+"单位(kg)");
double weight = reader.nextDouble();
System.out.print("请输入您的身高:"+"单位(米)");
double height = reader.nextDouble();
double BMI = weight/(height*height);
System.out.println("当期您的BMI是:"+BMI);
String a = (BMI < 18.5 ? "属于体重过轻":(BMI < 24?"属于正常范围":(BMI<27 ? "属于体重过重":(BMI < 30 ?"属于轻度肥胖":(BMI<35 ? "属于中度肥胖":"属于重度肥胖")))));
System.out.println(a);
}
}