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What's new in Java 11

 3 years ago
source link: https://marco.dev/java-11-newsworthy/
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What’s new in Java 11 (Open JDK)

Some of the new features in Java 11

In this page we will list some of the new features of Java 11 (from 9 to 11) relevant for the daily activity of business application developers.

Local-variable type inference

With Java 11 is possible to declare local variable with type inference with initializer (keyword var).

// words is of type String[]
var words = new String[] {"abc", "def"};

Assertions.assertTrue(words instanceof String[]);

// the initializer is mandatory
// dataList is of type ArrayList
var dataList = new ArrayList();

dataList.addAll(Arrays.asList(words));
Assertions.assertEquals("abc", dataList.get(0));
Assertions.assertEquals("def", dataList.get(1));

##Features in the String class lines A new method lines() creates a Stream with the lines of the String.

@Test
public void stringCountTest() {

  String text = "line 1\nline 2\nline3";

  // the new lines method return a Stream
  assertTrue(text.lines() instanceof Stream);

  // each element in the stream represents a line of the input string
  assertEquals(3, text.lines().count());
}

strip - stripLeading - stripTrailing strip eliminates the whitespaces at the beginning and at the end of a String.

@Test
public void stripTest() {
  
  String example = "      leading and trailing spaces      ";

  assertEquals("leading and trailing spaces", example.strip());
  assertEquals("leading and trailing spaces      ", example.stripLeading());
  assertEquals("      leading and trailing spaces", example.stripTrailing());
}

isBlank isBlank() returns true if the String is empty or it contains only whitespaces.

@Test
public void isBlankTest() {

  assertTrue("     ".isBlank());
  assertTrue("".isBlank());

}

repeat repeat composes a string repeating its content for a defined number of times.

@Test
public void repeatTest() {
  
  assertEquals("abc abc abc ", "abc ".repeat(3));
  assertEquals("", "abc ".repeat(0));

}

Optional

Optional get a new method to check if the value is not present: isEmpty()

@Test
public void isEmptyTest() {
  Optional<Integer> evaluate = Optional.of(5);
  Assertions.assertFalse(evaluate.isEmpty());
}

Author

Marco Molteni

Marco Molteni Blog


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