Converting String Array into Integer Array by accessing each indexes using loop

Question

I have my example code below. I'm trying to convert the gradeString into gradeInt and I can't seem to do it properly. When I print the value of gradeInt at the end using toString.

It says a blank array which is like this one: [ ]

Thanks for the help!

import java.util.*;

class testing{
    public static Scanner console = new Scanner(System.in);
    public static int studSize;
    public static String [] gradeArr = new String[studSize];
    public static int [] gradeInt = new int[gradeArr.length];

    public static void initialize(){
        System.out.print("Please enter student size: ");
        String studString = console.nextLine();
        studSize = Integer.parseInt(studString);
        enterData();
    }
    public static void enterData(){
        System.out.println("Enter student grades separated with dash(-)");
        System.out.print("Enter student grade/s: ");
        String gradeString = console.nextLine();
        gradeArr = gradeString.split("-");
        convert();
    }
    public static void convert(){
        for(int i=0; i<gradeInt.length; i++){
            gradeInt[i] = Integer.parseInt(gradeArr[i]);
        }
        print();
    }
    public static void print(){
        System.out.print(Arrays.toString(gradeArr));
        System.out.print(Arrays.toString(gradeInt));
    }
    public static void main(String [] args){
        initialize();
        //Main and Class Closing Braces
    }
}

I used methods for the overall context of the program. Please see my update post, thank you! — James Erin
– James Erin, Commented Feb 12, 2020 at 2:29
gradeInt is allocated based on the initial size of gradeArr which is 0. you'll need to allocate gradeInt after getting the size - which is a result of the split - so use gradeArr.lengthto size it - e.g. just before calling convert. — user2711811
– user2711811, Commented Feb 12, 2020 at 2:36

user2711811 · Accepted Answer · 2020-02-12 02:39:23Z

1

Add this line just before your call to convert for the "quick fix":

gradeInt = new int[gradeArr.length];

answered Feb 12, 2020 at 2:39

user2711811

Sign up to request clarification or add additional context in comments.

3 Comments

Scary Wombat Over a year ago

Like the quick_fix comment

James Erin Over a year ago

Thanks! So, I should re-declare gradeInt as a new object so that it'll continue.

user2711811 Over a year ago

No redeclare - you can however remove the static initialization and just initialize once as stated in answer. Similar with gradeArr - it is allocated by the "split" method.

Scary Wombat · Accepted Answer · 2020-02-12 02:37:58Z

0

Try this. The problem is that you are assigning sizes of arrays etc before any data is entered. Actually the usuage of studSize is not needed at all - see comments in code

public static Scanner console = new Scanner(System.in);
public static int studSize;
public static String [] gradeArr;
public static int [] gradeInt;

public static void initialize(){

    // not needed - 
    System.out.print("Please enter student size: ");
    String studString = console.nextLine();

    // not needed 
    studSize = Integer.parseInt(studString);
    enterData();
}
public static void enterData(){
    System.out.println("Enter student grades separated with dash(-)");
    System.out.print("Enter student grade/s: ");
    String gradeString = console.nextLine();
    gradeArr = gradeString.split("-");
    convert();
}
public static void convert(){
    // set here as the size is know
    gradeInt = new int[gradeArr.length];

    for(int i=0; i<gradeArr.length; i++){
        // should be carefull of NumberFormatException
        gradeInt[i] = Integer.parseInt(gradeArr[i]);
    }
    print();
}
public static void print(){
    System.out.print(Arrays.toString(gradeInt));
}
public static void main(String [] args){
    initialize();
    //Main and Class Closing Braces
}

edited Feb 12, 2020 at 2:37

answered Feb 12, 2020 at 2:11

Scary Wombat

44.9k7 gold badges38 silver badges67 bronze badges

3 Comments

UninformedUser Over a year ago

I'm wondering, shouldn't the TO get an exception if the split fails and the whole string will be parsed as integer?

James Erin Over a year ago

Ohhh. You're right! Thanks for the idea and answer.

James Erin Over a year ago

@UninformedUser. It does error, still trying to learn Java thoo. Anyways, thanks!

JavaBloxx · Accepted Answer · 2020-02-12 02:47:00Z

0

I ran your code and it works

Output:

[95, 85, 75]
Process finished with exit code 0

I suspect there may be an error in other parts of your code if you're getting a empty array.

What's the context you're running the code in? If you paste the rest of the code it might help finding the real source of the error.

SOLUTION:

Like Andy mentioned. The root error is contained here:

public static int [] gradeInt = new int[gradeArr.length];

You're defining this variable at runtime and assigning it the same length as gradeArr which is 0 at the time.

This results in a logic error that happens in the convert() method.

    for(int i=0; i<gradeInt.length; i++){
        gradeInt[i] = Integer.parseInt(gradeArr[i]);
    }

You are telling the code to loop if i was smaller than gradeInt which has a length of 0. Basically it never loops. It just skips the loop entirely.

The quickest way to fix this is to modify the code like this:

Don't assign a length to the gradeInt variable at runtime. Modify the line to this:

public static int [] gradeInt;

And then modify your enterData() method to this:

public static void enterData(){
    System.out.println("Enter student grades separated with dash(-)");
    System.out.print("Enter student grade/s: ");
    String gradeString = console.nextLine();
    gradeArr = gradeString.split("-");

    gradeInt = new int[gradeArr.length];
    convert();
}

edited Feb 12, 2020 at 2:47

answered Feb 12, 2020 at 2:14

JavaBloxx

311 gold badge1 silver badge6 bronze badges

2 Comments

James Erin Over a year ago

I used methods for the overall context of the program. Please see my update post, thank you!

JavaBloxx Over a year ago

Hey James I've found the error and posted the quickest fix. EDIT: Looks like Wombat beat me to it :)

Collectives™ on Stack Overflow

Converting String Array into Integer Array by accessing each indexes using loop

3 Answers 3

3 Comments

3 Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

3 Comments

3 Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related