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public class P2A7 

 public static void main(String args) 
 String name = args[0];
 int weight = Integer.parseInt(args[1]);
 double length = Double.parseDouble(args[2]);
 double bmi = weight / length * length;
 System.out.println(bmi);
 

Passing java Name 80 1.9 from the command line gives the output "80".
Why are the division and multiplication completely ignored?

Putting parentheses around "length * length" fixes this.

@Kristjan Link, This is because precedence of operator, when you write weight / (length * length) you increase precedence of multiplication *, because precedence of operator inside parentheses is always more than operator outside parentheses

Use of parentheses fix it because it increases precedence of * operator. By using parentheses you explicitly give * more precedence than / that's why multiplication expression will be executed first due to its increased precedence other wise both * and / have same precedence.

NOTE:

but remember despite same precedence / execute first than * because it comes first. Just like () is way to increase precedence, shifting position of operator is another way increase or decrease precedence of operators.The table present here. will be helpful for you in this regard.

Because double bmi = weight / length * length = weight is not same as
double bmi= weight / (length * length)

In the first case, You are ending up getting the same result as you are not using any parenthesis.

/ and * have equal precedence, so weight / length * length means (weight / length) * length

Because / has higher precedence than . Hence, your code just performs divide and multiply by length which returns weight. () has higher precedence than / and hence the code inside () will execute first which results in weight multiplied by lengthlength