删除Java String变量的最后一个字符

Question

A java String variable whose value is

String path = "http://cdn.gs.com/new/downloads/Q22010MVR_PressRelease.pdf.null"

I want to remove the last four characters ie, .null . Which method I can use in order to split.

Answer 1

I think you want to remove the last five characters ('.', 'n', 'u', 'l', 'l'):

path = path.substring(0, path.length() - 5);

Note how you need to use the return value - strings are immutable, so substring (and other methods) don't change the existing string - they return a reference to a new string with the appropriate data.

Or to be a bit safer:

if (path.endsWith(".null")) {
  path = path.substring(0, path.length() - 5);
}

However, I would try to tackle the problem higher up. My guess is that you've only got the ".null" because some other code is doing something like this:

path = name + "." + extension;

where extension is null. I would conditionalise that instead, so you never get the bad data in the first place.

(As noted in a question comment, you really should look through the String API . It's one of the most commonly-used classes in Java, so there's no excuse for not being familiar with it.)

Answer 2

import org.apache.commons.lang3.StringUtils;

// path = "http://cdn.gs.com/new/downloads/Q22010MVR_PressRelease.pdf.null"
StringUtils.removeEnd(path, ".null");
// path = "http://cdn.gs.com/new/downloads/Q22010MVR_PressRelease.pdf"

Answer 3

path = path.substring(0, path.length() - 5);

Answer 4

I am surprised to see that all the other answers (as of Sep 8, 2013) either involve counting the number of characters in the substring ".null" or throw a StringIndexOutOfBoundsException if the substring is not found. Or both :(

I suggest the following:

public class Main {

    public static void main(String[] args) {

        String path = "file.txt";
        String extension = ".doc";

        int position = path.lastIndexOf(extension);

        if (position!=-1)
            path = path.substring(0, position);
        else
            System.out.println("Extension: "+extension+" not found");

        System.out.println("Result: "+path);
    }

}

If the substring is not found, nothing happens, as there is nothing to cut off. You won't get the StringIndexOutOfBoundsException . Also, you don't have to count the characters yourself in the substring.

Answer 5

If you like to remove last 5 characters, you can use:

path.substring(0,path.length() - 5)

( could contain off by one error ;) )

If you like to remove some variable string:

path.substring(0,path.lastIndexOf('yoursubstringtoremove));

(could also contain off by one error ;) )

Answer 6

Another way:

if (s.size > 5) s.reverse.substring(5).reverse

BTW, this is Scala code. May need brackets to work in Java.