Detailed explanation of usage examples of java trim

The rim method is generally used to remove spaces, but according to the JDK API description, this method is not just about removing spaces, it can remove all characters from encoding '\u0000' to '\u0020'.

Carriage return and line feed are also among these 20 characters. The following is an example:

public 
class
 
String
Test {
public 
static
 void main(String[] args) {
char[] chars = {'a','b','c','\r','\n'};
System.out.
print
ln(chars.length);
String str = 
new
 String(chars);
System.out.println(str.length());
String newStr = str.
trim
();
System.out.println(newStr.length());
}
}

The output is as follows:

5
5
3

As can be seen from the output, the trimI() method also removes the two characters \r\n.

The following is the API description of the trim() method:

public String trim()

Returns a copy of the string, ignoring leading and trailing whitespace.

If this String object represents an empty character sequence, or the codes of the first and last characters of the character sequence represented by this String object are both greater than '\u0020' (space character), return this String A reference to the object.

Otherwise, if there is no character in the string with a code greater than ‘\u0020′, a new String object representing an empty string is created and returned.

Otherwise, assume k is the index of the first character with code greater than ‘\u0020′, and m is the index of the last character with code greater than ‘\u0020′. Creates a new String object that represents the substring of this string starting with the character at index k and ending with the character at index m, which is the result of this.substring(k, m+1).

This method is used to truncate whitespace from beginning to end of the string (as defined above).

Returns:
A copy of this string with leading and trailing whitespace removed, or a copy of this string if there are no leading and trailing whitespace.

The details of characters that can be removed by the trim() method can be output through the following function:

public class StringTest {
public static void main(String[] args) {
char[] chars = new char[20];
chars[0] = '\u0000';
chars[1] = '\u0001';
chars[2] = '\u0002';
chars[3] = '\u0003';
chars[4] = '\u0004';
chars[5] = '\u0005';
chars[6] = '\u0006';
chars[7] = '\u0007';
chars[8] = '\u0008';
chars[9] = '\u0009';
chars[10] = '\u0010';
chars[11] = '\u0012';
chars[12] = '\u0013';
chars[13] = '\u0014';
chars[14] = '\u0015';
chars[15] = '\u0016';
chars[16] = '\u0017';
chars[17] = '\u0018';
chars[18] = '\u0019';
chars[19] = '\u0020';
for
 (int i = 0; i < chars.length; i++) {
System.out.print("(" + i + ")" + chars[i] + "    ");
if
 (i != 0 && i % 5 == 0) {
System.out.println();
}
}
}
}

The output is as follows:

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