如何在 Java 中初始化长度为 0 的字符串数组？

Question

The Java Docs for the method
String[] java.io.File.list(FilenameFilter filter)
includes this in the returns description:

The array will be empty if the directory is empty or if no names were accepted by the filter.

How do I do a similar thing and initialize a String array (or any other array for that matter) to have a length 0?

Answer 1

As others have said,

new String[0]

will indeed create an empty array. However, there's one nice thing about arrays - their size can't change, so you can always use the same empty array reference. So in your code, you can use:

private static final String[] EMPTY_ARRAY = new String[0];

and then just return EMPTY_ARRAY each time you need it - there's no need to create a new object each time.

Answer 2

String[] str = new String[0]; ?

Answer 3

String[] str = {};

But

return {};

won't work as the type information is missing.

Answer 4

Ok I actually found the answer but thought I would 'import' the question into SO anyway

String[] files = new String[0];
or
int[] files = new int[0];

Answer 5

You can use ArrayUtils.EMPTY_STRING_ARRAY from org.apache.commons.lang3

import org.apache.commons.lang3.ArrayUtils;

    class Scratch {
        public static void main(String[] args) {
            String[] strings = ArrayUtils.EMPTY_STRING_ARRAY;
        }
    }

Answer 6

Make a function which will not return null instead return an empty array you can go through below code to understand.

    public static String[] getJavaFileNameList(File inputDir) {
    String[] files = inputDir.list(new FilenameFilter() {
        @Override
        public boolean accept(File current, String name) {
            return new File(current, name).isFile() && (name.endsWith("java"));
        }
    });

    return files == null ? new String[0] : files;
}

Answer 7

You can use following things-

1. String[] str = new String[0];
2. String[] str = ArrayUtils.EMPTY_STRING_ARRAY;<br>

Both are same.

Answer 8

All you have to do is

String str = "";
String[] newString = new String[str.length()];

This will give an empty String Array.

From my video

Thank you ItsPete! This answer is still important as it shows how the String is empty and how it works. For example, an int array cannot resize or change to another size because of that 0 that is an integer number. There will be an ArrayIndexOutOfBoundsException error. There must be a difference between String and int. However again, String has the double quotations and works to resize. Of course, it is a longer way. It still shows the reasoning between the int and mainly String.