Java 11 - New Methods in java.lang.String
Java 11, added various new methods in java.lang.String:
- String strip(): Returns a string whose value is this string, with all leading and trailing whitespace removed.
- String stripLeading(): Returns a string whose value is this string, with all leading whitespace removed.
- String stripTrailing(): Returns a string whose value is this string, with all trailing whitespace removed.
- boolean isBlank(): Returns true if the string is empty or contains only white space codepoints, otherwise false.
- Stream lines(): Returns a stream of lines extracted from this string, separated by line terminators.
- String repeat(int): Returns a string whose value is the concatenation of this string repeated count times.
There are several useful new methods here which can change our way when working with String. Let's take a look...
String::strip()
StringStrip.java
package com.dariawan.string;
public class StringStrip {
public static void main(String[] args) {
String s = " Java 11 features ";
System.out.printf("String: \"%s\"%n", s);
String striped = s.strip();
System.out.printf("strip(): \"%s\"%n", striped);
String stripLeft = s.stripLeading();
System.out.printf("stripLeading(): \"%s\"%n", stripLeft);
String stripRight = s.stripTrailing();
System.out.printf("stripTrailing(): \"%s\"%n", stripRight);
String trimmed = s.trim();
System.out.printf("trim(): \"%s\"%n", trimmed);
System.out.println("striped.equals(trimmed): " + striped.equals(trimmed));
System.out.println("Reason: ");
for (char c : s.toCharArray()) {
System.out.printf("'%s' ", String.valueOf((int) c));
}
}
}
Will produce following output:
String: " Java 11 features? " strip(): "Java 11 features" stripLeading(): "Java 11 features? " stripTrailing(): " Java 11 features" trim(): "Java 11 features?" striped.equals(trimmed): false Reason: '9' '32' '74' '97' '118' '97' '32' '49' '49' '32' '102' '101' '97' '116' '117' '114' '101' '115' '8195' '32'
You can see from the example above that String::strip and String::trim produced different result. This is because trim() only returns a string whose value is this string, with all leading and trailing space removed, where space is defined as any character whose codepoint is less than or equal to 'U+0020' (the space character).
There are three different whitespaces character in String " Java 11 features ":
- character tabulation: U+0009 (9)
- space: U+0020 (32)
- em space: U+2003 (8195)
Since trim() only remove any character whose codepoint is less than or equal to 'U+0020', in our case U+0009 and U+0020 will be removed, but U+2003 remain. All the whitespace characters are defined by Character::isWhitespace(char) and/or Character::isWhitespace(int) which is also defined String::isBlank()
String::isBlank()
StringBlank.java
package com.dariawan.string;
public class StringBlank {
public static void main(String[] args) {
String s = " ";
// isEmpty() method
System.out.println(s.isEmpty());
// isBlank() method
System.out.println(s.isBlank());
System.out.println("Characters: ");
for (char c : s.toCharArray()) {
System.out.printf("'%s' ", String.valueOf((int) c));
}
}
}
And the output is:
false true Characters: '32' '8197'
isBlank() also able to detect four-per-em space or U+2005 (decimal: 8197)
String::lines()
Using this new method, we can easily split a String instance into a Stream<String> of separate lines, separated by line terminators :
StringLines.java
package com.dariawan.string;
public class StringLines {
public static void main(String[] args) {
String s = "I eat every fruit.\rFruit is good for health.\r\nBut "
+ "I like durian most.\nDurian is "
+ "the king of fruits";
s.lines().forEach(System.out::println);
}
}
A line terminator is one of the following: a line feed character "\n" (U+000A), a carriage return character "\r" (U+000D), or a carriage return followed immediately by a line feed"\r\n" (U+000D U+000A).
String::repeat(int)
This is maybe the coolest additions to the String API in Java 11 release. String::repeat(int) allows concatenating a String with itself a given number of times:
StringRepeat.java
package com.dariawan.string;
public class StringRepeat {
public static void main(String[] args) {
String s = "pong ping";
System.out.printf("Repeat 5: \"%s\"%n", s.repeat(5));
System.out.printf("Repeat 0: \"%s\"%n", s.repeat(0));
System.out.printf("Repeat 0: \"%s\"%n", s.repeat(-5));
}
}
With output:
Repeat 5: "pong pingpong pingpong pingpong pingpong ping" Repeat 0: "" Exception in thread "main" java.lang.IllegalArgumentException: count is negative: -5 at java.base/java.lang.String.repeat(String.java:3149) at com.dariawan.string.StringRepeat.main(StringRepeat.java:9)
Repeat 0 times will return empty String, and repeat -5 will throw IllegalArgumentException "count is negative..."
Desson AriawanProgrammer