Adding to arrays and printing arrays in Java

Question

I need help figuring out how to get the user to input a number of integers no more than 10, and then add them to an array and print them out from the array. The code I have below, when run, asks the user for the integers and then runs forever and doesn't work. What am I doing wrong?

public static void main(String[] args) {

    Scanner input = new Scanner(System.in); // create a new scanner
    System.out.print("Enter integers between 1 and 100\n ");  
    int[] nextNumber = new int[10];
    int i = 0;
    int number = input.nextInt();

    while (i < nextNumber.length){
        i++;
        nextNumber[i] = number;
        number = input.nextInt();    
    }

    int a = 0;

    while (a  < nextNumber.length){
        a++;
        System.out.println(nextNumber[a]);   
    }

System.out.println(nextNumber[a]); You should a++ after the System.out.println(nextNumber[a]); — Nishant
– Nishant, Commented Oct 22, 2013 at 3:21
wasn't the problem, i had forgot to fix that from when i was experimenting with why it wont print. but even when the bottom line is System.out.println(nextNumber[a]); it still doesnt work — nfoggia
– nfoggia, Commented Oct 22, 2013 at 3:23
what do you mean by "does not work"? Also swap a++ and println — Nishant
– Nishant, Commented Oct 22, 2013 at 3:24
Add some print statements between steps, inside your while blocks if you need to. Or debug it in your IDE. Where is it looping forever? — Andrew
– Andrew, Commented Oct 22, 2013 at 3:36
No, nextNumber.length will be 10, because that's what you initialized it as, no matter how many elements are populated. — Andrew
– Andrew, Commented Oct 22, 2013 at 3:47

Bohemian · Accepted Answer · 2013-10-22 03:54:52Z

2

Seems to me like you increment your index too fast. You should increment your index variables at the end of your loops, not the beginning.

I would suggest you use for loops instead since they are designed for that:

Scanner input = new Scanner(System.in); // create a new scanner
System.out.print("Enter integers between 1 and 100\n ");

int[] nextNumber = new int[10];

for (int i = 0; i < nextNumber.length; i++){
    nextNumber[i] = input.nextInt();
}

for (int a = 0; a  < nextNumber.length; a++){
    System.out.println(nextNumber[1]);
}

Also, although I did not change it in the code, it seems like your last line should be:

System.out.println(nextNumber[a]);

edited Oct 22, 2013 at 3:54

Bohemian♦

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answered Oct 22, 2013 at 3:26

Francis

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Comments

Reimeus · Accepted Answer · 2013-10-22 03:24:14Z

1

Increment the array index after the values have been assigned to the arrays

while (i < nextNumber.length) {
    number = input.nextInt();
    nextNumber[i] = number;
    i++;
}

The same applys to the second loop

while (a < nextNumber.length) {
    System.out.println(nextNumber[a]);
    a++;
}

answered Oct 22, 2013 at 3:24

Reimeus

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2 Comments

nfoggia Over a year ago

still has the same problem. my program continues to run with nothing outputting to the screen

Reimeus Over a year ago

Actually the original problem was an ArrayIndexOutofBoundsException but worked just fine there, silly question: are you running the current version, clean/rebuild etc?

Prabhakaran Ramaswamy · Accepted Answer · 2013-10-22 03:29:24Z

0

Problem 1

Change

int i = 0;
int number = input.nextInt();
while (i < nextNumber.length){
i++;  //here is one problem. you not assigning the value to nextNumber[0].
nextNumber[i] = number;
number = input.nextInt();

}

to

int i = 0;
while (i < nextNumber.length){
   number = input.nextInt();
   nextNumber[i] = number;
   i++;  
}

Problem 2

change

int a = 0;
while (a  < nextNumber.length){
    a++;  //here is one problem ..You never get  nextNumber[0] value
System.out.println(nextNumber[a]);

}

to

int a = 0;
while (a  < nextNumber.length){
     System.out.println(nextNumber[a]);
    a++;
}

edited Oct 22, 2013 at 3:29

answered Oct 22, 2013 at 3:20

Prabhakaran Ramaswamy

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3 Comments

nfoggia Over a year ago

sorry, i noticed that too, but isn't the problem. Still doesnt run :/

nfoggia Over a year ago

still has the same problem. my program continues to run with nothing outputting to the screen

Prabhakaran Ramaswamy Over a year ago

@nfoggia you need to give 10 inputs one by one. type one number then press Enter key. do it 10 times

namalfernandolk · Accepted Answer · 2013-10-22 03:56:22Z

0

You can easily do this as follows. Better use for loop since you know the maximum number of iterations.

Scanner input = new Scanner(System.in); // create a new scanner
System.out.print("Enter integers between 1 and 100\n ");  
int[] nextNumber = new int[10];

int i = 0;
while (i < nextNumber.length)   nextNumber[i++] =  input.nextInt();


int a = 0;
while (a  < nextNumber.length)  System.out.println(nextNumber[a++]);

answered Oct 22, 2013 at 3:56

namalfernandolk

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2 Comments

Thomas W Over a year ago

Make it clear & correct first, long before you make it super-concise. I like the loop-body on a separate line; and definitely prefer advancement/increment to have it's own line for clarity. The OP here is a beginner, suggesting the most-terse C-style when he can't even place his increments correctly is not guiding him down the path to clear & simple correct code.

namalfernandolk Over a year ago

What you are saying is true Thomas. It can be simplify by separating them for line by line. But it does the same job. I wanted to illustrate the optimal code for his example.

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