Thread: Player input not working

Hello!

I'm making a BMI calculator but it's not working when I try to type in my height and weight.

this is the error I get

Exception in thread "main" java.lang.NumberFormatException: For input string: "1.72 59"
at java.base/jdk.internal.math.FloatingDecimal.readJavaFormatSt ring(FloatingDecimal.java:2054)
at java.base/jdk.internal.math.FloatingDecimal.parseDouble(Floa tingDecimal.java:110)
at java.base/java.lang.Double.parseDouble(Double.java:549)
at com.company.Main.main(Main.java:13)

String s = JOptionPane.showInputDialog("height and weight");
        int space = weight.indexOf(' ');
        int bar = height.indexOf(' ');
        String first = height.substring(0, space);
        String second = height.substring(space+1);
        String third = weight.substring(0, bar);
        String fourth = weight.substring(bar+2);
        double l = Double.parseDouble(s); //L is for height
        double b = Double.parseDouble(s); //b is for weight
        double bmi = Math.sqrt(l * l / b);
        JOptionPane.showMessageDialog(null, "your bmi" + bmi);

Thank you in advance

Exception in thread "main" java.lang.NumberFormatException: For input string: "1.72 59"

The String passed to the parseDouble method is not a valid double value. It looks like there are two values there separated by a space.
To get at the separate values in the String, read the user's response into a String and split it using the String class's split method.
Then work on each part separately.

Another option - have the user only enter one number at a time.
Otherwise describe how your instructor expects the program to get the user's input.

Ok. To use substring you need to know what columns to access. Did he say how to determine what columns to use with the substring method?
There are several useful methods in the String class:
indexOf to find the first space
lastIndexOf to find the last space

I assume there could be more than one space between the numbers.

Read the API doc for the class to see what they can do.

Does it work now?

If not, please post any further questions or problems.

"Exception in thread "main" java.lang.NumberFormatException: For input string: "59 1.72"

That looks like the original problem.

Did you use substring to get the two numbers from the input String?
Add some print statements that print out the two String values so you can see if the substring code was working.
When the two extracted Strings look good then try passing each one of them to the parseDouble method one at a time.

What is in the String: height? What is the value in space?
Print them out so you can see what their values are.

I suggest that you write a small test program with these 5 lines:
Define a String with two numbers: "333 444"
get the index of the space between the two numbers into an int
get the number before the space into a String using substring method
get the number after the space into a String using substring method
print out the value of the index, the value of the first String and the value of the second String

Did you try the test program I suggested?
That is how I check out new classes and methods - write a small test print and print out the results.

It would be useful if you made the test program and worked with it to learn how to use indexOf and substring. The posted code does not show what is in the String s or print out the value of space or bar or first or third so I can't say if anything is wrong with the code.

One problem I see is space-2? Why the value -2? What if the number has a different number of digits?
Same with space+5 What if the value is longer or shorter than expected? substring with a single value will return the String from that value to the end of the String.

Make the simple test program, compile it and execute it. If you have any questions about what it does, post the code and the full contents of the console from when you execute it. Add some comments asking your questions.