Java Array Iterator

Question

This is the example that I found online(I modified it) with a method that returns array. The array being passed is iterated to be a new array in a reversed order.

public class MultDim {
    public static void main(String[] args)
    {
        double[] myList = {1.9, 2.9, 3.4, 3.5};
        double[] returned = returnArr(myList);
        for (double elem : returned) {
            System.out.println(elem);
        }
    }

    public static double[] returnArr(double[] list) {
        double[] result = new double[list.length];
        for (int i = 0, j = list.length - 1; i < list.length; i++, j--) {
            result[j] = list[i];
        }
        return result;
    }
}

What I want is to pass the elements of the array being passed to the method to be in the same order in the array that is returned. Here is how I tried to solve it. But is returns an error which is(The primitive type int of list.length does not have a field i)

public class MultDim {
    public static void main(String[] args) {
        double[] myList = {1.9, 2.9, 3.4, 3.5};
        double[] returned = returnArr(myList);
        for (double elem : returned) {
            System.out.println(elem);
        }
    }


    public static double[] returnArr(double[] list) {
        double[] result = new double[list.length];
        for (int i = 0, j = 0; j < list.length, i < list.length; i++, j++) {
            result[j] = list[i];
        }
        return result;
    }
}

I am just wondering what I concept missed from this.

I suspect the problem is this part: j < list.length, i < list.length - I imagine that's expected to only ever be a single boolean condition. That said, since both i and j are going to be the same value, and list and result will both have the same length, you can get rid of j entirely: for(int i = 0; i < list.length; i++) {result[i] = list[i];}. — Anthony Grist
– Anthony Grist, Commented Dec 22, 2014 at 14:05
And if he wants anyway to check i and j: j < list.length && i < list.length — Paco Abato
– Paco Abato, Commented Dec 22, 2014 at 14:08

armnotstrong · Accepted Answer · 2014-12-22 14:07:21Z

2

stop condition in the for loop can't write as this

for(int i = 0, j = 0; j < list.length, i < list.length; i++, j++)

in this situation a simple

for(int i = 0, j = 0; i < list.length; i++, j++)

is good enough

or just:

for(int i=0; i<list.length; i++){
     result[i] = list[i];
}

answered Dec 22, 2014 at 14:07

armnotstrong

9,18518 gold badges70 silver badges137 bronze badges

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

4 Comments

wintenbb Over a year ago

new is a reserved keyword

armnotstrong Over a year ago

sorry for that, I just edit it while you are posting

Tadele Ayelegn Over a year ago

@armnotstrong so I am not supposed to put two conditions that way. thank you for the solution.

armnotstrong Over a year ago

yes, the stop condition required to be a boolean expression

M A · Accepted Answer · 2014-12-22 14:07:32Z

1

The compiler error is due to the condition in the for loop. j < list.length, i < list.length is an invalid condition. If you meant both j < list.length and i < list.length, then use the logical AND operator (&&):

j < list.length && i < list.length

Having said this, you don't need to use both i and j in the loop since the returned array has the same size as the array passed as an argument. So you could just do with:

for (int i = 0; i < list.length; i++) {
    result[i] = list[i];
}

answered Dec 22, 2014 at 14:07

M A

73.2k14 gold badges149 silver badges182 bronze badges

Comments

wintenbb · Accepted Answer · 2014-12-22 14:16:41Z

1

You should take a look on how a for needs to be constructed

for (init; stop_condition; actions)

init can be a list of java initialisation, separated with comma (,)

stop_condition needs to be a single java expression that evaluates to a boolean, in your case it should be :

j < list.length && i < list.length

action can be a list of java expressions, separated with comma (,)

way more simple you could write (as i and j are always the same):

for(int i = 0;i < list.length; i++)
{
    result[j] = list[i];
}

edited Dec 22, 2014 at 14:16

answered Dec 22, 2014 at 14:08

wintenbb

4,1663 gold badges32 silver badges44 bronze badges

Comments

Mohammadreza Khatami · Accepted Answer · 2014-12-22 14:46:31Z

0

the code's in first image will reverse array fields but this is yours and will worked!

public class MultDim {
 public static void main(String[] args) {
    double[] myList = {1.9, 2.9, 3.4, 3.5};
    double[] returned = returnArr(myList);
    for (double elem : returned) {
        System.out.println(elem);
    }
}


 public static double[] returnArr(double[] list) {
    double[] result = new double[list.length];
    for (int i = 0, j = 0; j < list.length && i < list.length; i++, j++) {
        result[j] = list[i];
    }
    return result;
  }
}

answered Dec 22, 2014 at 14:46

Mohammadreza Khatami

1,3322 gold badges14 silver badges29 bronze badges

Comments

wassgren · Accepted Answer · 2014-12-22 14:55:21Z

0

To solve the actual problem - how to copy array data you should probably use the functions provided by the Java libraries.

Example:

final double[] copy1 = Arrays.copyOf(myList, myList.length);

Other options include System.arraycopy.

answered Dec 22, 2014 at 14:55

wassgren

19.3k6 gold badges66 silver badges79 bronze badges

Collectives™ on Stack Overflow

Java Array Iterator

5 Answers 5

4 Comments

Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

4 Comments

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related