在数组列表Java中分割字符串

Question

I have an ArrayList consisting of dates. All of the dates are in this format:

"day month time timezone year". An example would look like this, Wed Aug 10:15:17 AST 2016 .

I need to split the string at the second ":". Here is my code to do that.

int dateSize = date.size();
int i = 0;
ArrayList<String> splitDate = new ArrayList<String>();
splitDate.clear();
while(i < dateSize) {
    String[] splitString = date.get(i).split(":" + 1);
    splitDate.add(splitString[0]);
    Log.i("info", String.valueOf(splitDate));
    i++;
}

The ArrayList consists about 50 items. At first, this code works. It prints this to the log,

Wed Sep 14 23:30 , which is what I want.

But then, at random, it starts to print this,

Wed Sep 14 23:30, Wed Sep 14 23:24:36 AST 2016, Wed Sep 14 23, Wed Sep 14 22, Wed Sep 14 22, Tue Sep 13 22, Tue Sep 13 22, Tue Sep 13 22:07:33 AST 2016, Mon Sep 12 20

Sometimes it splits the second ":", sometimes it splits the first ":", sometimes it doesn't split anything. I cannot figure out why this is happening. IF I change my code to this,

String[] splitString = date.get(i).split(":");
splitDate.add(splitString[0]);

It works flawlessly. Everything gets printed to the log like this, Wed Aug 10 , no exceptions.

Is my approach correct?

Answer 1

Ok, first of all this isn't what you want

String[] splitString = date.get(i).split(":" + 1);

This is splitting on the String ":1"

What you want to do is split on ":" and then get the first two entries in the array and concatenate them

String[] splitString = date.get(i).split(":");
splitDate.add(splitString[0] + ":" + splitString[1]);

Answer 2

As one of the comments says you problem is this line

String[] splitString = date.get(i).split(":" + 1);

Essentially you're going to be passing ":1" as the argument to split(). Therefore you'll end up selecting severything up tot he first instance of ":1", or the whole string if ":1" isn't present. For example:

• Wed Aug 10 :15:17 AST 2016 will give Wed Aug 10
• Wed Aug 10:25 :17 AST 2016 will give Wed Aug 10:25
• Wed Aug 10:25:25 AST 2016 will give Wed Aug 10:25:25 AST 2016

If you know thee format of the string then I'd just do:

String dateStr = date.substring(0, 13)

If you don't know the format of the strings (eg they've been typed in by a user who may have typoed some) then I'd check them with a regex.

Answer 3

If you have the an array element of strings in the format "Wed Aug 10:15:17 AST 2016" and you split/delimit by ":", you will end up with the following array of strings:

[0] Wed Aug 10
[1] 15
[2] 17 AST 2016

If you look at the above array, you cannot accomplish your desired output of "Wed Aug 10 15:17" with just splitting the string and then adding the components (ie: You will miss the '17' in the above example, as it falls in element [2]).

I am not a Java dev, so the syntax may be a bit off, but if you want to generate "Wed Aug 10 15:17", then I believe you are looking for this:

String[] splitString = date.get(i).split(":");\\remove "1" from your delimiter
String tempString = splitString[2].substring(0,1);
splitDate.add(splitString[0] + " " + splitString[1] + ":" + tempString);

In the above snippet, the tempString line is getting the first two characters from the split string array element [2]. You then add the first two array elements with the tempString (ie: 17) and get your output.

Edit: I just wanted to mention that if you have control over the input of date strings, I would advise using a different delimiter. Using ":" causes the issue that the delimiter also exists as a valid, non-delimiter, character in the string. The above code snippet should work presuming the input is not controlled by you/your method.

Answer 4

A bit more complicated way using replaceFirst method.

ArrayList<String> splitDate = new ArrayList<String>();
for (String dateItem : date) {
    String output = dateItem.replaceFirst("^(\\w{3}\\s\\w{3}\\s\\d{2}:\\d{2}):\\d{2}\\s\\w+\\s\\d+$", "$1");
    splitDate.add(output);
    Log.i("info", output);  
}

Answer 5

You can always use the java.util.StringTokenizer class. Considering date is the ArrayList containing dates in String format, the following lines of code will add the date in the format required.

StringTokenizer dateString = new StringTokenizer(date.get(i), ":");
splitDate.add(dateString.nextToken() + ":" + dateString.nextToken());

Simple enough!