From Java 9, Oracle will release a new version of Java every 6 months, starting with Java 10, which is to be released on march 20, 2018.
This blog highlights the major language and API changes in Java 10.
Local variable type inference
For local variables, specifying the type is not always needed anymore.
//java 9 String text = "Hello World"; //java 10 var text = "Hello World";
The Java compiler will infer the type of the variable from the right-hand side of the statement.
This will also work on method calls:
//assuming that myMethod returns a String var stringResult = myMethod();
You can also use this on for loops:
//local variables in for loops
var stringList = List.of("a", "b", "c");
for (var element: stringList) {
System.out.println(element);
}
for (var i = 0; i < 10; i++) {
System.out.println(i);
}
Local variable type inference won’t compile in the following cases:
//won't compile, no type can be determined
var x;
//won't compile on method reference
var name2 = Main::getName;
//won't compile on null reference
var nullValue = null;
//won't compile on array initializer
var stringArray = {1, 2};
A word of caution
Correctly naming variables becomes even more important when using local variable type inference, so State Your Intentions when introducing a variable!
API changes
The List, Set and Map interfaces now support copy methods which return unmodifiable collection copies.
//java 9 List newList = Collections.unmodifiableList(oldList); //java 10 List newList = List.copyOf(oldList);
Collectors now also support collecting to unmodifiable collections for List, Set and Map.
//java 9 List newList = Collections.unmodifiableList(oldList.stream().collect(Collectors.toList())); //java 10 List newList = oldList.stream().collect(Collectors.toUnmodifiableList());
