Java 9

Installation of Java 9

Mac

Don't use jenv, it doesn't work well... If you want to work with 2 versions of java and switch between them depending on the project: (example with java 8 and java 9)

Install java 8
Install java 9
Switch between versions using:
- export JAVA_HOME=`/usr/libexec/java_home -v 1.8`
- export JAVA_HOME=`/usr/libexec/java_home -v 1.9`

protip: put these aliases in your .bashrc or .zshrc or whatever shell you use to easily switch between java versions

alias java8='export JAVA_HOME=$(/usr/libexec/java_home -v 1.8)'
alias java9='export JAVA_HOME=$(/usr/libexec/java_home -v 9)'
java8

This last part will make sure the default is currently java 8 (because by default the java version used is always the last installed one). Now we still need to find a way to switch versions ‘persistently’ because executing java9 only switches the version for the current terminal.

Java 9 factory methods for collections

What does this new feature do?

Makes it easier to create instances of collections and maps with small numbers of elements. New static factory methods on the List, Set, and Map interfaces make it simpler to create immutable instances of those collections.

What are the benefits/disadvantages?

Improved readability
Less object initialization
Less boiler plate code

Do you like the feature?

Yes, see above

Will you use it on your project?

Absolutely

What are the reasons you won’t be using it?

The resulting collections will be immutable. If you want to do mutations to collections, you won't be able to use this feature

Example

Java8:

List<String> list3 = Collections.unmodifiableList(Stream.of("a", "b", "c").collect(toList()));

Java9:

    public static void main(String[] args){
        List<String> fruits = List.of("apple", "orange", "banana");
        for (String fruit: fruits) {
            System.out.println(fruit);
        }
        try {
            fruits.add("pear");
        } catch (UnsupportedOperationException uoe) {
            System.err.println("unable to modify fruits list");
        }

        Set<String> marbles = Set.of("aggie", "alley", "steely");
        for (String marble: marbles) {
            System.out.println(marble);
        }
            
        try {
            marbles.add("swirly");
        } catch (UnsupportedOperationException uoe) {
            System.err.println("unable to modify marbles set");
        }
    }

SoftwareSandbox/java-9-factory-methods-collections