[quote = "javaeye"] [size = medium] because it is a web crawling work, quite often it is the processing of the string. JAVA is so commonly used classes in the String class, Pattern class, Matcher the class. trim where the String class () matches the methods and Matcher class () method, let's say something about their role and local attention.
[/size][/quote]

The following test class code

class A{

	public static void main(String[] args) {
		A a=new A();
		a.testTrim();
		a.testRegex();
	}

	public void testTrim(){
		String str[]=new String[4];
		str[0]="　this is test method trim　";
		str[1]=" this is test method trim ";
		str[2]="\t this is test method trim \t";
		str[3]=" \r\n this is test method trim \r\n\t ";
		System.out.println ( "Here is detected in String trim () function removes those characters: \ n");
		for (int i = 0; i < str.length; i++) {
			System.out.println("|"+str[i].trim()+"|");
		}
	}

	public void testRegex(){
		String str[]=new String[4];
		str[0]="\r\naaaaAAaaa\r\n";
		str[1]=" aaaaBBaaa ";
		str[2]="　aaaaCCaaa　";
		str[3]="\taaaaDDaaa\t";
		Pattern p=Pattern.compile(".*([A-Z]{2}).*");
		System.out.println ( "\ n each array element is not added trim () is a function of the result after: \ n");
		for (int i = 0; i < str.length; i++) {
			Matcher matcher=p.matcher(str[i]);
			if(matcher.matches()){
				System.out.println ( "first match" + i + "element, its value is:" + matcher.group (1));
			}
			else{
				System.out.println ( "Matching" + i + "failed element");
			}
		}
		System.out.println ( "\ n plus each array element trim () is a function of the result after: \ n");
		for (int i = 0; i < str.length; i++) {
			Matcher matcher=p.matcher(str[i].trim());
			if(matcher.matches()){
				System.out.println ( "first match" + i + "element, its value is:" + matcher.group (1));
			}
			else{
				System.out.println ( "Matching" + i + "failed element");
			}
		}
	}
}

// Here are the results of running the code:

Here is to detect the String trim () function removes those characters:

|　this is test method trim　|
|this is test method trim|
|this is test method trim|
|this is test method trim|

Not every array element plus trim () is a function of the result after:

0 matching element failure
The first matching element, which value is: BB
The second matching element, which value is: CC
The third matching element, which value is: DD

Plus trim on each array element () is a function of the result after:

0 matched elements whose value is: AA
The first matching element, which value is: BB
The second matching element, which value is: CC
The third matching element, which value is: DD

[Quote = "javaeye"] [size = medium] From the above results, we can see:

[Color = red] 1.trim () method is a full-size space can not be removed at both ends of the string, i.e., Chinese space

2.matches string matching methods can not contain a line feed and carriage return. [/ Size] [/ color] [/ quote]