Java的。 如何删除数组上的空白区域

Question

For example I split a string "+name" by +. I got an white space" " and the "name" in the array(this doesn't happen if my string is "name+").

t="+name";
String[] temp=t.split("\\+");

the above code produces

temp[0]=" "
temp[1]=name

I only wants to get "name" without whitespace..

Also if t="name+" then temp[0]=name. I'm wondering what is difference between name+ and +name. Why do I get different output.

Answer 1

simply loop thru the items in array like the one below and remove white space

for (int i = 0; i < temp.length; i++){
    temp[i] = if(!temp[i].trim().equals("") || temp[i]!=null)temp[i].trim();
}

Answer 2

The value of the first array item is not a space ( " " ) but an empty string ( "" ) . The following snippet demonstrates the behaviour and provides a workaround: I simply strip leading delimiters from the input. Note, that this should never be used for processing csv files, because a leading delimiter will create an empty column value which is usually wanted.

    for (String s : "+name".split("\\+")) {
        System.out.printf("'%s'%n", s);
    }

    System.out.println();

    for (String s : "name+".split("\\+")) {
        System.out.printf("'%s'%n", s);
    }

    System.out.println();

    for (String s : "+name".replaceAll("^\\+", "").split("\\+")) {
        System.out.printf("'%s'%n", s);
    }

Answer 3

You get the extra element for "+name" 's case is because of non-empty value "name" after the delimiter.

The split() function only "trims" the trailing delimiters that result to empty elements at the end of an array. See JavaSE Manual .

Examples of .split("\\\\+") output:

"+++++"     = { }                // zero length array because all are trailing delimiters
"+name+"    = { "", "name" }     // trailing delimiter removed
"name+++++" = { "name" }         // trailing delimiter removed
"name+"     = { "name" }         // trailing delimiter removed
"++name+"   = { "", "", "name" } // trailing delimiter removed

---

I would suggest preventing to have those extra delimiters on both ends rather than cleaning up afterwards.

Answer 4

删除空白区域

str.replaceAll("\\W","").

Answer 5

 String yourString = "name +"; yourString = yourString.replaceAll("\\\\W", ""); yourArray = yourString.split("\\\\+"); 

Answer 6

For a one liner :

String temp[] = t.replaceAll("(^\\++)?(\\+)?(\\+*)?", "$2").split("\\+");

This will replace all multiple plus signs by one, or a plus sign at the start by empty String, and then split on plus signs. Which will basically eliminate empty Strings in the result.

split(String regex) is equivalent to split(String regex, int limit) with limit = 0. And the documentation of the latter states :

If n is zero then the pattern will be applied as many times as possible, the array can have any length, and trailing empty strings will be discarded.

Which is why a '+' at the start works differently than a '+' at the end

Answer 7

You might want to give guavas Splitter a try. It has a nice fluent api to deal with emptyStrings, trim(), etc.

@Test
public void test() {
    final String t1 = "+name";
    final String t2 = "name+";

    assertThat(split(t1), hasSize(1));
    assertThat(split(t1).get(0), is("name"));

    assertThat(split(t2), hasSize(1));
    assertThat(split(t2).get(0), is("name"));
}

private List<String> split(final String sequence) {
    final Splitter splitter = Splitter.on("+").omitEmptyStrings().trimResults();
    return Lists.newArrayList(splitter.split(sequence));
}