Reverse numbers using java arrays

Question

Hello I am new to java and am trying to do this assignment but I can't get the needed output which is the reverse order of the numbers. Can any one help me what I am missing? Thank you so much! My Code's output looks like this:

How many floating point numbers do you want to type: 5 Type in 1. number: 5,4 Type in 2. number: 6 Type in 3. number: 7,2 Type in 4. number: -5 Type in 5. number: 2

Given numbers in reverse order:

Assignment

Create a program that asks the user how many floating point numbers he wants to give. After this the program asks the numbers, stores them in an array and prints the contents of the array in reverse order.

Program is written to a class called ReverseNumbers. Example output

How many floating point numbers do you want to type: 5 Type in 1. number: 5,4 Type in 2. number: 6 Type in 3. number: 7,2 Type in 4. number: -5 Type in 5. number: 2

Given numbers in reverse order: 2.0 -5.0 7.2 6.0 5.4

My code:

    import java.util.Scanner;  
public class apples {  
    public static void main(String[] args) {  
        Scanner reader = new Scanner(System.in);  

        double[] numbers;  

        System.out.print("How many floating point numbers do you want to type: ");  
        int size = reader.nextInt();  
        numbers = new double[size];  

        for (int i=0; i < numbers.length; i++) {  
            System.out.print("Type in "+(i+1)+". number:");  
            numbers[i-1] = reader.nextDouble();  

        }  

        System.out.println();  
        System.out.println("Given numbers in reverse order:");  

        for (int i=numbers.length-1; i <= 0; i--) {  

              System.out.println( numbers[i]);  
        }  
    }  
}

numbers[i-1] would throw an IndexOutOfBounds exception. Change it just to numbers[i]. — Obicere
– Obicere, Commented Feb 27, 2014 at 5:13

Christian Tapia · Accepted Answer · 2014-02-27 05:12:59Z

3

The second for loop condition is wrong. It should be:

for (int i = numbers.length - 1; i >= 0; i--)

because i <= 0 won't be true if numbers.length - 1 is greater than 0, therefore your for loop won't run its body.

Also in the first for loop, the index of numbers are wrong. It should be:

numbers[i] = reader.nextDouble();

This is because if i = 0, then numbers[i - 1] will be numbers[-1], and that's an invalid index.

answered Feb 27, 2014 at 5:12

Christian Tapia

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1 Comment

Christian Tapia Over a year ago

No problem. Feel free to accept this answer if it was useful and solved your problem: How does accepting an answer work

ItachiUchiha · Accepted Answer · 2014-02-27 05:18:57Z

1

In the first loop you are using i+1 and not i++, so the value of i is never incremented. So, your

numbers[i-1] becomes numbers[-1], which should throw an error. I am astonished, now your program is even giving you an output !

Try this

for (int i=0; i < numbers.length; i++) {  
        System.out.print("Type in "+(i+1)+". number:");  
        //numbers[i-1] = reader.nextDouble();  
        numbers[i] = reader.nextDouble(); 
    }

and in second loop. You are checking from last to first so i>=0 instead of i<=0

for (int i=numbers.length-1; i >= 0; i--) {  
          System.out.println( numbers[i]);  
    }

edited Feb 27, 2014 at 5:18

answered Feb 27, 2014 at 5:13

ItachiUchiha

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Comments

Nathan Tuggy · Accepted Answer · 2017-05-14 06:03:46Z

0

int[] numbers;
System.out.print("How many integer point numbers do you want to type: ");
int size = reader.nextInt();
numbers = new int[size];

for (int i=0; i < size; i++) {
    //System.out.print("Type in "+(i+1)+". number:");
    numbers[i] = reader.nextInt();
}

System.out.println();
System.out.println("Given numbers in reverse order:");

for (int i=size-1; i >= 0; i--) {
      System.out.print( numbers[i]);
}

edited May 14, 2017 at 6:03

Nathan Tuggy

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answered May 14, 2017 at 5:28

Gowsy

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