Java -- String. split () function, javastring. split

Java -- String. split () function, javastring. split
In java doc, there are String [] java. lang. String. split (String regex)

Splits this string around matches of the given regular expression.

This method works as if by invoking the two-argumentsplitMethod with the given expression and a limit argument of zero. Trailing empty strings are therefore not supported ded in the resulting array.

The string"Boo: and: foo", For example, yields the following results with these expressions:

 
 

  
  
 
   
 
    
Regex
 
    
Result
 
   
 
   
 
    
:
 
    
{ "boo", "and", "foo" }
 
   
 
   
 
    
o
 
    
{ "b", "", ":and:f" }
 
   
 
  
 
 

Parameters:

RegexThe delimiting regular expression

Returns:

The array of strings computed by splitting this string around matches of the given regular expression

Throws:

PatternSyntaxException-if the regular expression's syntax is invalid

Since:

1.4

See Also:

Java. util. regex. Pattern

@ Spec

JSR-51

Note the following:

(1) If "." is used as the separator, String. split ("\.") must be written as follows.

String. split (".");

For example, this Code:

String str="123.456";String []arrStr=str.split(".");System.out.println(arrStr.length);

Result:

String str = "123.456"; String [] arrStr = str. split ("\."); System. out. println (arrStr. length );

Result:

　

The reason is:

Splits this string around matches of the given regular expression. It requires a regular expression, so it must meet the regular expression form,

Therefore, escape is required.

The source code of the split () function is provided below for your reference:

 public String[] split(String regex, int limit) {        /* fastpath if the regex is a         (1)one-char String and this character is not one of the            RegEx's meta characters ".$|()[{^?*+\\", or         (2)two-char String and the first char is the backslash and            the second is not the ascii digit or ascii letter.         */        char ch = 0;        if (((regex.value.length == 1 &&             ".$|()[{^?*+\\".indexOf(ch = regex.charAt(0)) == -1) ||             (regex.length() == 2 &&              regex.charAt(0) == '\\' &&              (((ch = regex.charAt(1))-'0')|('9'-ch)) < 0 &&              ((ch-'a')|('z'-ch)) < 0 &&              ((ch-'A')|('Z'-ch)) < 0)) &&            (ch < Character.MIN_HIGH_SURROGATE ||             ch > Character.MAX_LOW_SURROGATE))        {            int off = 0;            int next = 0;            boolean limited = limit > 0;            ArrayList<String> list = new ArrayList<>();            while ((next = indexOf(ch, off)) != -1) {                if (!limited || list.size() < limit - 1) {                    list.add(substring(off, next));                    off = next + 1;                } else {    // last one                    //assert (list.size() == limit - 1);                    list.add(substring(off, value.length));                    off = value.length;                    break;                }            }            // If no match was found, return this            if (off == 0)                return new String[]{this};            // Add remaining segment            if (!limited || list.size() < limit)                list.add(substring(off, value.length));            // Construct result            int resultSize = list.size();            if (limit == 0)                while (resultSize > 0 && list.get(resultSize - 1).length() == 0)                    resultSize--;            String[] result = new String[resultSize];            return list.subList(0, resultSize).toArray(result);        }        return Pattern.compile(regex).split(this, limit);    }

Public String [] split (String regex ){
Return split (regex, 0 );
}

 

What is the use of the split function of the String class in java? Are the first and last elements of the array output after I split the string empty?

It is useless. Just a few lines of code that you can run on your own.
String aa = "a, B, c, d, e, f ";
String [] bb = aa. split (",");
For (int I = 0; I <bb. length; I ++ ){
System. out. println (bb [I]);
}

Java code: Use of split

The parameter of the split function is not a string but a regular expression.
+ The number itself is a special character in a regular expression and needs to be escaped.
String [] array = str. split ("\\+ ");