CODEWITHSUNDEEP
javainputknapsack-problem
user8581463
user8581463

Reputation: 19

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

I am working on the knapsack problem, I am new to Java. I am able to add numbers manually like this in the main: 

 // Fill the bag of weights. 
 //myWeights.bagOfWeights.add(18);
 //myWeights.bagOfWeights.add(2);
 //System.out.println("Possible answers: ");
 //myWeights.fillKnapSack(20);

However, I am not able to allow the user to input the numbers.
The first number should be the target followed by the weights.
So I have tried to take the user input as a string and split it up with whitespace, and then convert it to an integer.
Next, I tried to do the parseInt 2 ways, but I was unsuccessful both way.
Here is the code: 

import java.util.*;
 
  public class KnapSackWeights{
 
    private Sack bagOfWeights = new Sack();
    private Sack knapSack = new Sack();
 
    public static void main(String[] args){
        KnapSackWeights myWeights = new KnapSackWeights();
        Scanner in = new Scanner(System.in);
        System.out.println("Enter the input:");
        String input = in.nextLine();
        String[] sar = input.split(" ");
        //System.out.println(inp);
        int target = Integer.parseInt(input);
        System.out.println(target);
        
        int[] weights_array = new int[26];
        
        int n = input.length()-1;
        for(int i=1; i<=n; i++)
        {
           weights_array[i - 1] = Integer.parseInt(sar[i]);
        }
        int k = weights_array[0];
        myWeights.bagOfWeights.add(target);
        //System.out.println(target);
        System.out.println("Possible answers: ");
        myWeights.fillKnapSack(k);
        //myWeights.fillKnapSack(Integer.parseInt(sar[0]));

        // Fill the bag of weights. 
        //myWeights.bagOfWeights.add(11);
        //myWeights.bagOfWeights.add(8);
        //myWeights.bagOfWeights.add(7);
        //myWeights.bagOfWeights.add(6);
        //myWeights.bagOfWeights.add(5);
        //myWeights.bagOfWeights.add(4);
        
        //System.out.println("Possible answers: ");
        //myWeights.fillKnapSack(20);
    }

Here is the error:

Exception in thread "main" java.lang.NumberFormatException: For input string: "18 7 4 6" at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65) at java.lang.Integer.parseInt(Integer.java:580) at java.lang.Integer.parseInt(Integer.java:615) at KnapSackWeights.main(KnapSackWeights.java:18)

Thanks for your help.

Upvotes: 1

Views: 32626

Answers (2)

Nash
Nash

Reputation: 1

maybe this could be helpful


        //your input
        String input = "18 7 4 6";
        //split into string array by space
        String[] split = input.split(" ");
        int[] nums = new int[split.length];
        //parse each string into number
        for (int i = 0; i < split.length; i++) {
            nums[i] = Integer.parseInt(split[i]);
        }
        System.out.println(Arrays.toString(nums));

Upvotes: -1

Overleaf
Overleaf

Reputation: 925

You are calling the parseInt method with the String 18 7 4 6. Since this isn't a valid Integer, the NumberFormatException is thrown.

You are already splitting the input into the String[] sar. In the for loop you already call parseInt on each value in sar, which are valid Integers. Seems like you have everything in place; just remove the int target = Integer.parseInt(input); line.

Upvotes: 0

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