CommandLine Arguments in java Help

Question

I'm suppose to use Command-Line Arguments to take user input and than use an enhanced for loop to sum.

This is the error:

Exception in thread "main" java.lang.Error: Unresolved compilation problem: Type mismatch: cannot convert from double to int

public class EnhanceForLoop {


public static void main(String[] args) {
    // TODO Auto-generated method stub

    if(args.length !=5)
        System.out.println(" please enter no more than 4 numbers");
    else
    {

    double sum; 
    double arrayLength = Double.parseDouble(args[0]);
    double [] myArray = new double [ arrayLength ];

    double value = Double.parseDouble((args[1]));
    double counter = Double.parseDouble((args[2]));


    for(double num: myArray)
      sum += num;


    System.out.printf("The sum is %f ", sum);

    }

}

}

here is how it is so far:

public class EnhanceForLoop {

public static void main(String[] args) {
    // TODO Auto-generated method stub

    if(args.length !=5)
        System.out.println(" please enter no more than 4 numbers");
    else
    {

    double sum = 0.0; 

    int arrayLength = Integer.parseInt(args[0]);
    double [] myArray = new double [ arrayLength ];

    double num1 = Double.parseDouble((args[1]));
    double num2 = Double.parseDouble((args[2]));
    double num3 = Double.parseDouble((args[3]));
    double num4 = Double.parseDouble((args[4]));
    double num5 = Double.parseDouble((args[5]));


    for(double num: myArray)
      sum += num;


    System.out.printf("The sum is %f ", sum);

    }

}

}

Here is the answer:

public class EnhanceForLoop {

public static void main(String[] args) {
    // TODO Auto-generated method stub

    if(args.length !=5)
        System.out.println(" please enter no more than 4 numbers");
    else
    {

    double sum = 0.0; 

    int arrayLength = Integer.parseInt(args[0]);
    double [] myArray = new double [ arrayLength ];

    double num1 = Double.parseDouble((args[1]));
    double num2 = Double.parseDouble((args[2]));
    double num3 = Double.parseDouble((args[3]));
    double num4 = Double.parseDouble((args[4]));



    for(String s: args){
        sum += Double.parseDouble(s);
    }
      System.out.println("Sum: "+sum);
    }




}

}

You can't create an array with new double[arrayLength] unless arrayLength is an integer. — Chris Nash
– Chris Nash, Commented Feb 23, 2011 at 23:00
so, and now you can delete the superfluous code from your solution, about everything else than the loop and the System.out.println after it. — Paŭlo Ebermann
– Paŭlo Ebermann, Commented Feb 24, 2011 at 1:32

Jim Garrison · Accepted Answer · 2011-02-23 22:58:25Z

4

arrayLength must be an integer. Thus

int arrayLength = Integer.parseInt(args[0]);
double [] myArray = new double [ arrayLength ];

answered Feb 23, 2011 at 22:58

Jim Garrison

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2 Comments

hooch Over a year ago

In this line: double [] myArray = new double [ arrayLength ]; the constructor for an array takes only ints as argument. cast it to an int

Mugetsu Over a year ago

Thanks, I fix that but unfortunately another problem appeared: when I compile the sum was 0.000000

Jason Sendros · Accepted Answer · 2011-02-23 23:12:20Z

3

It's also important to remember to think about the flow of your code:

You initialize an array. You sum the values in the array.

You never added values to the array, so you will always be summing a bunch of zeros.

answered Feb 23, 2011 at 23:12

Jason Sendros

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1 Comment

Mugetsu Over a year ago

can you help me add with the enhance for loop

Paŭlo Ebermann · Accepted Answer · 2011-02-24 00:05:28Z

2

You are summing up an array filled with 0.0 (as this is the default value), not the command line arguments.

If you want to sum the arguments, you have to iterate over them (=the args array), convert each argument to a double, and add these up. You don't need the double[] at all.

Edit: (after some comments)

In your example code of your question you are using an enhanced for-loop of an array, so it seems you know what such a loop is. So, now use the args array instead of your myArray there. Inside the loop, you do the Integer.parseInt(...) or Double.parseDouble or similar, and add the result to your sum variable.

If you need more than one statement in the loop, use { ... } to group them.

edited Feb 24, 2011 at 0:05

answered Feb 23, 2011 at 23:21

Paŭlo Ebermann

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5 Comments

Mugetsu Over a year ago

[code]public static void main(String[] args) { int sum; int num1 = Integer.parseInt(args[0]); int num2 = Integer.parseInt(args[1]); sum = num1 + num2; System.out.printf("The sum is %d ", sum); } }[/code]

Paŭlo Ebermann Over a year ago

@Mugetsu: Don't add code in a comment (it is not readable here), add it to your question (if it is needed to understand it) - it has an edit link.

Mugetsu Over a year ago

I'm supposed to use an enhance for loop to sum the numbers and I know how to do when I store the numbers like: `code' int sum; int num1 = Integer.parseInt(args[0]); int num2 = Integer.parseInt(args[1]); sum = num1 + num2; System.out.printf("The sum is %d ", sum);

Mugetsu Over a year ago

how can i use the args array?

Paŭlo Ebermann Over a year ago

@Mugetsu: Put it at the place where you are using myArray now.

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