How to use java.util.Scanner class to read input?

Question

I have a question about using java.util.Scanner class to read input.

Below is my coding without using java.util.Scanner class to read input:

         public class NewTry {
          public static float[][] clone(float[][] a) throws Exception {
          float b[][] = new float[a.length][a[0].length];

           for (int i = 0; i < a.length; i++) {
            for (int j = 0; j < a[0].length; j++) {
                b[i][j] = a[i][j];
              }
           }
           return b;
         }

         public static void main(String args[]) {


          float[][] a = new float[][] { { 1.513f, 2.321f, 3.421f }, { 4.213f, 5.432f, 6.123f },
        { 7.214f, 8.213f, 9.213f } };



          try {
    float b[][] = clone(a);
    for (int i = 0; i < a.length; i++) {
        for (int j = 0; j < a[0].length; j++) {
            System.out.print(b[i][j] + " ");
        }
         System.out.println();
          }
      } catch (Exception e) {
          System.out.println("Error!!!");
    }
        }
    }

Show output without using java.util.Scanner:

      run:
     1.513 2.321 3.421 
     4.213 5.432 6.123 
     7.214 8.213 9.213 
     BUILD SUCCESSFUL (total time: 3 seconds)

My problem is how to add java.util.Scanner class to read input without default float number in the coding? Is using array run scanner?

Actually I want the sample output same like the below （the float number must key in myself）：

       run:
       Type nine float numbers two-dimensional array of similar type and size with line breaks, end 
       by"-1":
       1.513
       2.321
       3.421 
       4.213
       5.432 
       6.123 
       7.214
       8.213 
       9.213 
       -1


       The result is:

       1.513 2.321 3.421 
       4.213 5.432 6.123 
       7.214 8.213 9.213 
       BUILD SUCCESSFUL (total time: 11 second)

Hope someone can guide me or modified my coding to add java.util.Scanner class to read input .Thanks.

How to put a Scanner input into an array… for example a couple of numbers — Abra
– Abra, Commented Oct 24, 2019 at 10:27
@Abra Ok. Can you modify my code to add Scanner class? Thanks. — user11337935
– user11337935, Commented Oct 24, 2019 at 10:44

Ioannis Barakos · Accepted Answer · 2019-10-24 10:47:44Z

1

Check this out

 public static void main(String args[]) {

            Scanner sc = new Scanner (System.in);
            System.out.println ("Type nine float numbers two-dimensional array of similar type and size with line breaks, end by -1:");
            float[][] a = new float[3][3];
            for (int i=0; i<3; i++){
                for (int j=0; j<3; j++){
                    String line = sc.nextLine();
                    if ("-1".equals(line)){
                        break;
                    }
                    a[i][j]=Float.parseFloat(line);
                }
            }

            System.out.println("\n The result is:");

            try {
                float b[][] = clone(a);
                for (int i = 0; i < a.length; i++) {
                    for (int j = 0; j < a[0].length; j++) {
                        System.out.print(b[i][j] + " ");
                    }
                    System.out.println();
                }
            } catch (Exception e) {
                System.out.println("Error!!!");
            }
        }

You should define a new Scanner (sc) and then loop 3 x 3 times until you read all input. If the user enters -1 the loop ends. Note that you do not need to exit when 9 numbers are entered.

Also each user input is read as a line and not as a token, and then is parsed into a Float. If the user enters a String that is not a float number then it throws an Exception.

Sample:

Type nine float numbers two-dimensional array of similar type and size with line breaks, end by -1:
1.1
1.2
1.3
2.1
2.2
2.3
3.1
3.2
3.3

The result is:
1.1 1.2 1.3 
2.1 2.2 2.3 
3.1 3.2 3.3

answered Oct 24, 2019 at 10:47

Ioannis Barakos

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2 Comments

user11337935 Over a year ago

@loannis Barakos how to stop limit in the array?

Ioannis Barakos Over a year ago

If you want to insert numbers infinitely until the -1 is entered, the simplest way is to set your 2d array length with a maximum number e.g. [1000][3]. Then the for loop's i should be increased to 1000 (or .length). When -1 is entered you can store i into a var so you know that the array is filled up to i. Another solution would be to create a 2d Arraylist. Example java2blog.com/2d-arraylist-java-example

Abhishek pruthvi V M · Accepted Answer · 2019-10-24 10:26:05Z

0

Scanner scan =new Scanner(System.in);
float[][] a = new float[3][3];

for(int i =0 ;i<3;i++) {
   for(int j=0; j<3; i++) {
      a[i][j] =scan.Float();
   }
}

answered Oct 24, 2019 at 10:26

Abhishek pruthvi V M

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2 Comments

user11337935 Over a year ago

Can you add your answer in my coding? Thanks.

kenny_k Over a year ago

Thank you for your answer - although code/config snippets might provide some limited short-term help, a proper explanation would greatly improve its long-term value by showing why this is a good solution to the problem, and would make it more useful to future readers with other, similar questions. Please edit your answer to add some explanation, including the assumptions you've made.

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