CODEWITHSUNDEEP
java
Ioanna Kardasi
Ioanna Kardasi

Reputation: 11

What's the issue with Length()?

I have a java project for uni and this is my code. I have a problem with Length(). Can please anyone help me and spot m mistakes? Thank you in advance. 

package mytest;

import java.io.File;

public class MyTest {

public static void main(String[] args) {

    File here = new File("");
    File[] contents = here.listFiles();

    for (int counter = 0; counter < contents.Length(); counter++) {
    System.out.println(contents[counter].getName());
    }

    File directory = here getParentDirectory();
    System.out.println("The absolute path is" + directory.getAbsolutePath());
    File[] list = directory.listFiles(); 
    System.out.println("Directrory code contains" + list.Length() + "items\n."); 

    System.out.println("----\n");

    for (int i = 0; i < list.Length(); i++) {
        if (list[i].isDirectory())  {
            System.out.println(list[i].getName() + "is a directory with" + list[i].listFiles.Length + "elements"); 

        } else {
            System.out.println(list[i].getName() + "has a size of" + list[i].Length() + "bytes.");
        }
    }
}
}

Upvotes: 0

Views: 74

Answers (4)

skypjack
skypjack

Reputation: 50540

The issue is that you haven't read carefully what the documentation says:

Finally, you can use the built-in length property to determine the size of any array.

The proposed example is:

System.out.println(anArray.length);

In that case, length is not a method, instead it's a built-in property of any array. Because of that, trying to invoke it will result in an error.

Upvotes: 1

Abdelhak
Abdelhak

Reputation: 8387

For array should use

contents.length ;

But for string use this

 contents.length();

Let me first highlight the different way for similar purpose.

length --- arrays (int[], double[], String[]) ---- to know the length of the arrays.

length() --- String related Object (String, StringBuilder etc)to know the length of the String

Upvotes: 0

A_Di-Matteo
A_Di-Matteo

Reputation: 27812

When working on an array you need to use the .length field, there is no method Length(). You can replace in your code .Length() by .length and it should then be fine.

Be also aware however that on the last System.out statement, in the else block of the loop, the array is of type File[], hence each element is a File. A File has a method length() (lower care) which provides the length of the file as a long.

Moreover, in the if block of the loop, the File element of the array provides the method listFiles() (and not a field .listFiles) which is an array and as such, again, it has a field, length, giving you the length of the array.

We hence have:

  • An array, providing a field, length
  • A File, having a method, length(), for its size
  • A method of the File class, listFiles() which returns an array of File

Here is the fully compiling (fixed) code:

public static void main(String[] args) {

    File here = new File("");
    File[] contents = here.listFiles();

    for (int counter = 0; counter < contents.length; counter++) {
        System.out.println(contents[counter].getName());
    }

    File directory = here.getParentFile();
    System.out.println("The absolute path is" + directory.getAbsolutePath());
    File[] list = directory.listFiles();
    System.out.println("Directrory code contains" + list.length + "items\n.");

    System.out.println("----\n");

    for (int i = 0; i < list.length; i++) {
        if (list[i].isDirectory()) {
            System.out.println(list[i].getName() + "is a directory with" + list[i].listFiles().length + "elements");

        } else {
            System.out.println(list[i].getName() + "has a size of" + list[i].length() + "bytes.");
        }
    }
}

Upvotes: 2

LaurensVijnck
LaurensVijnck

Reputation: 552

There is a big distinction between between the .Length(), a class method and the primitive type .length. While using strings, we use the .Length() as a class method. Since Strings are stored in classes in the background. To find the length of an array use the .length; as this actually searches inside the heap memory. If you like some more information on the background reason for this, I suggest you to check the following link.

http://www.programcreek.com/2013/04/what-does-a-java-array-look-like-in-memory/

Upvotes: 0

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